/* Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ /* Cashing of files with only does (sequential) read or writes of fixed- length records. A read isn't allowed to go over file-length. A read is ok if it ends at file-length and next read can try to read after file-length (and get a EOF-error). Possibly use of asyncronic io. macros for read and writes for faster io. Used instead of FILE when reading or writing whole files. This code makes mf_rec_cache obsolete (currently only used by ISAM) One can change info->pos_in_file to a higher value to skip bytes in file if also info->read_pos is set to info->read_end. If called through open_cached_file(), then the temporary file will only be created if a write exeeds the file buffer or if one calls my_b_flush_io_cache(). If one uses SEQ_READ_APPEND, then two buffers are allocated, one for reading and another for writing. Reads are first done from disk and then done from the write buffer. This is an efficient way to read from a log file when one is writing to it at the same time. For this to work, the file has to be opened in append mode! Note that when one uses SEQ_READ_APPEND, one MUST write using my_b_append ! This is needed because we need to lock the mutex every time we access the write buffer. TODO: When one SEQ_READ_APPEND and we are reading and writing at the same time, each time the write buffer gets full and it's written to disk, we will always do a disk read to read a part of the buffer from disk to the read buffer. This should be fixed so that when we do a my_b_flush_io_cache() and we have been reading the write buffer, we should transfer the rest of the write buffer to the read buffer before we start to reuse it. */ #include "mysys_priv.h" #include "my_sys.h" #include #include #include "my_thread_local.h" #include "mysql/psi/mysql_file.h" PSI_file_key key_file_io_cache; #define lock_append_buffer(info) \ mysql_mutex_lock(&(info)->append_buffer_lock) #define unlock_append_buffer(info) \ mysql_mutex_unlock(&(info)->append_buffer_lock) #define IO_ROUND_UP(X) (((X)+IO_SIZE-1) & ~(IO_SIZE-1)) #define IO_ROUND_DN(X) ( (X) & ~(IO_SIZE-1)) /* Setup internal pointers inside IO_CACHE SYNOPSIS setup_io_cache() info IO_CACHE handler NOTES This is called on automaticly on init or reinit of IO_CACHE It must be called externally if one moves or copies an IO_CACHE object. */ void setup_io_cache(IO_CACHE* info) { /* Ensure that my_b_tell() and my_b_bytes_in_cache works */ if (info->type == WRITE_CACHE) { info->current_pos= &info->write_pos; info->current_end= &info->write_end; } else { info->current_pos= &info->read_pos; info->current_end= &info->read_end; } } static void init_functions(IO_CACHE* info) { enum cache_type type= info->type; switch (type) { case READ_NET: /* Must be initialized by the caller. The problem is that _my_b_net_read has to be defined in sql directory because of the dependency on THD, and therefore cannot be visible to programs that link against mysys but know nothing about THD, such as myisamchk */ break; case SEQ_READ_APPEND: info->read_function = _my_b_seq_read; info->write_function = 0; /* Force a core if used */ break; default: info->read_function = info->share ? _my_b_read_r : _my_b_read; info->write_function = _my_b_write; } setup_io_cache(info); } /* Initialize an IO_CACHE object SYNOPSIS init_io_cache_ext() info cache handler to initialize file File that should be associated to to the handler If == -1 then real_open_cached_file() will be called when it's time to open file. cachesize Size of buffer to allocate for read/write If == 0 then use my_default_record_cache_size type Type of cache seek_offset Where cache should start reading/writing use_async_io Set to 1 of we should use async_io (if avaiable) cache_myflags Bitmap of different flags MY_WME | MY_FAE | MY_NABP | MY_FNABP | MY_DONT_CHECK_FILESIZE file_key Instrumented file key for temporary cache file RETURN 0 ok # error */ int init_io_cache_ext(IO_CACHE *info, File file, size_t cachesize, enum cache_type type, my_off_t seek_offset, pbool use_async_io, myf cache_myflags, PSI_file_key file_key) { size_t min_cache; my_off_t pos; my_off_t end_of_file= ~(my_off_t) 0; DBUG_ENTER("init_io_cache_ext"); DBUG_PRINT("enter",("cache: 0x%lx type: %d pos: %ld", (ulong) info, (int) type, (ulong) seek_offset)); info->file= file; info->file_key= file_key; info->type= TYPE_NOT_SET; /* Don't set it until mutex are created */ info->pos_in_file= seek_offset; info->pre_close = info->pre_read = info->post_read = 0; info->arg = 0; info->alloced_buffer = 0; info->buffer=0; info->seek_not_done= 0; if (file >= 0) { pos= mysql_file_tell(file, MYF(0)); if ((pos == (my_off_t) -1) && (my_errno() == ESPIPE)) { /* This kind of object doesn't support seek() or tell(). Don't set a flag that will make us again try to seek() later and fail. */ info->seek_not_done= 0; /* Additionally, if we're supposed to start somewhere other than the the beginning of whatever this file is, then somebody made a bad assumption. */ DBUG_ASSERT(seek_offset == 0); } else info->seek_not_done= MY_TEST(seek_offset != pos); } info->disk_writes= 0; info->share=0; if (!cachesize && !(cachesize= my_default_record_cache_size)) DBUG_RETURN(1); /* No cache requested */ min_cache=use_async_io ? IO_SIZE*4 : IO_SIZE*2; if (type == READ_CACHE || type == SEQ_READ_APPEND) { /* Assume file isn't growing */ if (!(cache_myflags & MY_DONT_CHECK_FILESIZE)) { /* Calculate end of file to avoid allocating oversized buffers */ end_of_file= mysql_file_seek(file, 0L, MY_SEEK_END, MYF(0)); /* Need to reset seek_not_done now that we just did a seek. */ info->seek_not_done= end_of_file == seek_offset ? 0 : 1; if (end_of_file < seek_offset) end_of_file=seek_offset; /* Trim cache size if the file is very small */ if ((my_off_t) cachesize > end_of_file-seek_offset+IO_SIZE*2-1) { cachesize= (size_t) (end_of_file-seek_offset)+IO_SIZE*2-1; use_async_io=0; /* No need to use async */ } } } cache_myflags &= ~MY_DONT_CHECK_FILESIZE; if (type != READ_NET && type != WRITE_NET) { /* Retry allocating memory in smaller blocks until we get one */ cachesize= ((cachesize + min_cache-1) & ~(min_cache-1)); for (;;) { size_t buffer_block; /* Unset MY_WAIT_IF_FULL bit if it is set, to prevent conflict with MY_ZEROFILL. */ myf flags= (myf) (cache_myflags & ~(MY_WME | MY_WAIT_IF_FULL)); if (cachesize < min_cache) cachesize = min_cache; buffer_block= cachesize; if (type == SEQ_READ_APPEND) buffer_block *= 2; if (cachesize == min_cache) flags|= (myf) MY_WME; if ((info->buffer= (uchar*) my_malloc(key_memory_IO_CACHE, buffer_block, flags)) != 0) { info->write_buffer=info->buffer; if (type == SEQ_READ_APPEND) info->write_buffer = info->buffer + cachesize; info->alloced_buffer=1; break; /* Enough memory found */ } if (cachesize == min_cache) DBUG_RETURN(2); /* Can't alloc cache */ /* Try with less memory */ cachesize= (cachesize*3/4 & ~(min_cache-1)); } } DBUG_PRINT("info",("init_io_cache: cachesize = %lu", (ulong) cachesize)); info->read_length=info->buffer_length=cachesize; info->myflags=cache_myflags & ~(MY_NABP | MY_FNABP); info->request_pos= info->read_pos= info->write_pos = info->buffer; if (type == SEQ_READ_APPEND) { info->append_read_pos = info->write_pos = info->write_buffer; info->write_end = info->write_buffer + info->buffer_length; mysql_mutex_init(key_IO_CACHE_append_buffer_lock, &info->append_buffer_lock, MY_MUTEX_INIT_FAST); } #if defined(SAFE_MUTEX) else { /* Clear mutex so that safe_mutex will notice that it's not initialized */ memset(&info->append_buffer_lock, 0, sizeof(info->append_buffer_lock)); } #endif if (type == WRITE_CACHE) info->write_end= info->buffer+info->buffer_length- (seek_offset & (IO_SIZE-1)); else info->read_end=info->buffer; /* Nothing in cache */ /* End_of_file may be changed by user later */ info->end_of_file= end_of_file; info->error=0; info->type= type; init_functions(info); DBUG_RETURN(0); } /* init_io_cache_ext */ /* Initialize an IO_CACHE object SYNOPSIS init_io_cache() - Wrapper for init_io_cache_ext() NOTE This function should be used if the IO_CACHE tempfile is not instrumented. */ int init_io_cache(IO_CACHE *info, File file, size_t cachesize, enum cache_type type, my_off_t seek_offset, pbool use_async_io, myf cache_myflags) { return init_io_cache_ext(info, file, cachesize, type, seek_offset, use_async_io, cache_myflags, key_file_io_cache); } /* Use this to reset cache to re-start reading or to change the type between READ_CACHE <-> WRITE_CACHE If we are doing a reinit of a cache where we have the start of the file in the cache, we are reusing this memory without flushing it to disk. */ my_bool reinit_io_cache(IO_CACHE *info, enum cache_type type, my_off_t seek_offset, pbool use_async_io MY_ATTRIBUTE((unused)), pbool clear_cache) { DBUG_ENTER("reinit_io_cache"); DBUG_PRINT("enter",("cache: 0x%lx type: %d seek_offset: %lu clear_cache: %d", (ulong) info, type, (ulong) seek_offset, (int) clear_cache)); /* One can't do reinit with the following types */ DBUG_ASSERT(type != READ_NET && info->type != READ_NET && type != WRITE_NET && info->type != WRITE_NET && type != SEQ_READ_APPEND && info->type != SEQ_READ_APPEND); /* If the whole file is in memory, avoid flushing to disk */ if (! clear_cache && seek_offset >= info->pos_in_file && seek_offset <= my_b_tell(info)) { /* Reuse current buffer without flushing it to disk */ uchar *pos; if (info->type == WRITE_CACHE && type == READ_CACHE) { info->read_end=info->write_pos; info->end_of_file=my_b_tell(info); /* Trigger a new seek only if we have a valid file handle. */ info->seek_not_done= (info->file != -1); } else if (type == WRITE_CACHE) { if (info->type == READ_CACHE) { info->write_end=info->write_buffer+info->buffer_length; info->seek_not_done=1; } info->end_of_file = ~(my_off_t) 0; } pos=info->request_pos+(seek_offset-info->pos_in_file); if (type == WRITE_CACHE) info->write_pos=pos; else info->read_pos= pos; } else { /* If we change from WRITE_CACHE to READ_CACHE, assume that everything after the current positions should be ignored */ if (info->type == WRITE_CACHE && type == READ_CACHE) info->end_of_file=my_b_tell(info); /* flush cache if we want to reuse it */ if (!clear_cache && my_b_flush_io_cache(info,1)) DBUG_RETURN(1); info->pos_in_file=seek_offset; /* Better to do always do a seek */ info->seek_not_done=1; info->request_pos=info->read_pos=info->write_pos=info->buffer; if (type == READ_CACHE) { info->read_end=info->buffer; /* Nothing in cache */ } else { info->write_end=(info->buffer + info->buffer_length - (seek_offset & (IO_SIZE-1))); info->end_of_file= ~(my_off_t) 0; } } info->type=type; info->error=0; init_functions(info); DBUG_RETURN(0); } /* reinit_io_cache */ /* Read buffered. SYNOPSIS _my_b_read() info IO_CACHE pointer Buffer Buffer to retrieve count bytes from file Count Number of bytes to read into Buffer NOTE This function is only called from the my_b_read() macro when there isn't enough characters in the buffer to satisfy the request. WARNING When changing this function, be careful with handling file offsets (end-of_file, pos_in_file). Do not cast them to possibly smaller types than my_off_t unless you can be sure that their value fits. Same applies to differences of file offsets. When changing this function, check _my_b_read_r(). It might need the same change. RETURN 0 we succeeded in reading all data 1 Error: couldn't read requested characters. In this case: If info->error == -1, we got a read error. Otherwise info->error contains the number of bytes in Buffer. */ int _my_b_read(IO_CACHE *info, uchar *Buffer, size_t Count) { size_t length,diff_length,left_length, max_length; my_off_t pos_in_file; DBUG_ENTER("_my_b_read"); /* If the buffer is not empty yet, copy what is available. */ if ((left_length= (size_t) (info->read_end-info->read_pos))) { DBUG_ASSERT(Count >= left_length); /* User is not using my_b_read() */ memcpy(Buffer,info->read_pos, left_length); Buffer+=left_length; Count-=left_length; } /* pos_in_file always point on where info->buffer was read */ pos_in_file=info->pos_in_file+ (size_t) (info->read_end - info->buffer); /* Whenever a function which operates on IO_CACHE flushes/writes some part of the IO_CACHE to disk it will set the property "seek_not_done" to indicate this to other functions operating on the IO_CACHE. */ if (info->seek_not_done) { if ((mysql_file_seek(info->file, pos_in_file, MY_SEEK_SET, MYF(0)) != MY_FILEPOS_ERROR)) { /* No error, reset seek_not_done flag. */ info->seek_not_done= 0; } else { /* If the seek failed and the error number is ESPIPE, it is because info->file is a pipe or socket or FIFO. We never should have tried to seek on that. See Bugs#25807 and #22828 for more info. */ DBUG_ASSERT(my_errno() != ESPIPE); info->error= -1; DBUG_RETURN(1); } } /* Calculate, how much we are within a IO_SIZE block. Ideally this should be zero. */ diff_length= (size_t) (pos_in_file & (IO_SIZE-1)); /* If more than a block plus the rest of the current block is wanted, we do read directly, without filling the buffer. */ if (Count >= (size_t) (IO_SIZE+(IO_SIZE-diff_length))) { /* Fill first intern buffer */ size_t read_length; if (info->end_of_file <= pos_in_file) { /* End of file. Return, what we did copy from the buffer. */ info->error= (int) left_length; DBUG_RETURN(1); } /* Crop the wanted count to a multiple of IO_SIZE and subtract, what we did already read from a block. That way, the read will end aligned with a block. */ length=(Count & (size_t) ~(IO_SIZE-1))-diff_length; if ((read_length= mysql_file_read(info->file,Buffer, length, info->myflags)) != length) { /* If we didn't get, what we wanted, we either return -1 for a read error, or (it's end of file), how much we got in total. */ info->error= (read_length == (size_t) -1 ? -1 : (int) (read_length+left_length)); DBUG_RETURN(1); } Count-=length; Buffer+=length; pos_in_file+=length; left_length+=length; diff_length=0; } /* At this point, we want less than one and a partial block. We will read a full cache, minus the number of bytes, we are within a block already. So we will reach new alignment. */ max_length= info->read_length-diff_length; /* We will not read past end of file. */ if (info->type != READ_FIFO && max_length > (info->end_of_file - pos_in_file)) max_length= (size_t) (info->end_of_file - pos_in_file); /* If there is nothing left to read, we either are done, or we failed to fulfill the request. Otherwise, we read max_length into the cache. */ if (!max_length) { if (Count) { /* We couldn't fulfil the request. Return, how much we got. */ info->error= (int)left_length; DBUG_RETURN(1); } length=0; /* Didn't read any chars */ } else if ((length= mysql_file_read(info->file,info->buffer, max_length, info->myflags)) < Count || length == (size_t) -1) { /* We got an read error, or less than requested (end of file). If not a read error, copy, what we got. */ if (length != (size_t) -1) memcpy(Buffer, info->buffer, length); info->pos_in_file= pos_in_file; /* For a read error, return -1, otherwise, what we got in total. */ info->error= length == (size_t) -1 ? -1 : (int) (length+left_length); info->read_pos=info->read_end=info->buffer; DBUG_RETURN(1); } /* Count is the remaining number of bytes requested. length is the amount of data in the cache. Read Count bytes from the cache. */ info->read_pos=info->buffer+Count; info->read_end=info->buffer+length; info->pos_in_file=pos_in_file; memcpy(Buffer, info->buffer, Count); DBUG_RETURN(0); } /* Prepare IO_CACHE for shared use. SYNOPSIS init_io_cache_share() read_cache A read cache. This will be copied for every thread after setup. cshare The share. write_cache If non-NULL a write cache that is to be synchronized with the read caches. num_threads Number of threads sharing the cache including the write thread if any. DESCRIPTION The shared cache is used so: One IO_CACHE is initialized with init_io_cache(). This includes the allocation of a buffer. Then a share is allocated and init_io_cache_share() is called with the io cache and the share. Then the io cache is copied for each thread. So every thread has its own copy of IO_CACHE. But the allocated buffer is shared because cache->buffer is the same for all caches. One thread reads data from the file into the buffer. All threads read from the buffer, but every thread maintains its own set of pointers into the buffer. When all threads have used up the buffer contents, one of the threads reads the next block of data into the buffer. To accomplish this, each thread enters the cache lock before accessing the buffer. They wait in lock_io_cache() until all threads joined the lock. The last thread entering the lock is in charge of reading from file to buffer. It wakes all threads when done. Synchronizing a write cache to the read caches works so: Whenever the write buffer needs a flush, the write thread enters the lock and waits for all other threads to enter the lock too. They do this when they have used up the read buffer. When all threads are in the lock, the write thread copies the write buffer to the read buffer and wakes all threads. share->running_threads is the number of threads not being in the cache lock. When entering lock_io_cache() the number is decreased. When the thread that fills the buffer enters unlock_io_cache() the number is reset to the number of threads. The condition running_threads == 0 means that all threads are in the lock. Bumping up the number to the full count is non-intuitive. But increasing the number by one for each thread that leaves the lock could lead to a solo run of one thread. The last thread to join a lock reads from file to buffer, wakes the other threads, processes the data in the cache and enters the lock again. If no other thread left the lock meanwhile, it would think it's the last one again and read the next block... The share has copies of 'error', 'buffer', 'read_end', and 'pos_in_file' from the thread that filled the buffer. We may not be able to access this information directly from its cache because the thread may be removed from the share before the variables could be copied by all other threads. Or, if a write buffer is synchronized, it would change its 'pos_in_file' after waking the other threads, possibly before they could copy its value. However, the 'buffer' variable in the share is for a synchronized write cache. It needs to know where to put the data. Otherwise it would need access to the read cache of one of the threads that is not yet removed from the share. RETURN void */ void init_io_cache_share(IO_CACHE *read_cache, IO_CACHE_SHARE *cshare, IO_CACHE *write_cache, uint num_threads) { DBUG_ENTER("init_io_cache_share"); DBUG_PRINT("io_cache_share", ("read_cache: 0x%lx share: 0x%lx " "write_cache: 0x%lx threads: %u", (long) read_cache, (long) cshare, (long) write_cache, num_threads)); DBUG_ASSERT(num_threads > 1); DBUG_ASSERT(read_cache->type == READ_CACHE); DBUG_ASSERT(!write_cache || (write_cache->type == WRITE_CACHE)); mysql_mutex_init(key_IO_CACHE_SHARE_mutex, &cshare->mutex, MY_MUTEX_INIT_FAST); mysql_cond_init(key_IO_CACHE_SHARE_cond, &cshare->cond); mysql_cond_init(key_IO_CACHE_SHARE_cond_writer, &cshare->cond_writer); cshare->running_threads= num_threads; cshare->total_threads= num_threads; cshare->error= 0; /* Initialize. */ cshare->buffer= read_cache->buffer; cshare->read_end= NULL; /* See function comment of lock_io_cache(). */ cshare->pos_in_file= 0; /* See function comment of lock_io_cache(). */ cshare->source_cache= write_cache; /* Can be NULL. */ read_cache->share= cshare; read_cache->read_function= _my_b_read_r; read_cache->current_pos= NULL; read_cache->current_end= NULL; if (write_cache) write_cache->share= cshare; DBUG_VOID_RETURN; } /* Remove a thread from shared access to IO_CACHE. SYNOPSIS remove_io_thread() cache The IO_CACHE to be removed from the share. NOTE Every thread must do that on exit for not to deadlock other threads. The last thread destroys the pthread resources. A writer flushes its cache first. RETURN void */ void remove_io_thread(IO_CACHE *cache) { IO_CACHE_SHARE *cshare= cache->share; uint total; DBUG_ENTER("remove_io_thread"); /* If the writer goes, it needs to flush the write cache. */ if (cache == cshare->source_cache) flush_io_cache(cache); mysql_mutex_lock(&cshare->mutex); DBUG_PRINT("io_cache_share", ("%s: 0x%lx", (cache == cshare->source_cache) ? "writer" : "reader", (long) cache)); /* Remove from share. */ total= --cshare->total_threads; DBUG_PRINT("io_cache_share", ("remaining threads: %u", total)); /* Detach from share. */ cache->share= NULL; /* If the writer goes, let the readers know. */ if (cache == cshare->source_cache) { DBUG_PRINT("io_cache_share", ("writer leaves")); cshare->source_cache= NULL; } /* If all threads are waiting for me to join the lock, wake them. */ if (!--cshare->running_threads) { DBUG_PRINT("io_cache_share", ("the last running thread leaves, wake all")); mysql_cond_signal(&cshare->cond_writer); mysql_cond_broadcast(&cshare->cond); } mysql_mutex_unlock(&cshare->mutex); if (!total) { DBUG_PRINT("io_cache_share", ("last thread removed, destroy share")); mysql_cond_destroy (&cshare->cond_writer); mysql_cond_destroy (&cshare->cond); mysql_mutex_destroy(&cshare->mutex); } DBUG_VOID_RETURN; } /* Lock IO cache and wait for all other threads to join. SYNOPSIS lock_io_cache() cache The cache of the thread entering the lock. pos File position of the block to read. Unused for the write thread. DESCRIPTION Wait for all threads to finish with the current buffer. We want all threads to proceed in concert. The last thread to join lock_io_cache() will read the block from file and all threads start to use it. Then they will join again for reading the next block. The waiting threads detect a fresh buffer by comparing cshare->pos_in_file with the position they want to process next. Since the first block may start at position 0, we take cshare->read_end as an additional condition. This variable is initialized to NULL and will be set after a block of data is written to the buffer. RETURN 1 OK, lock in place, go ahead and read. 0 OK, unlocked, another thread did the read. */ static int lock_io_cache(IO_CACHE *cache, my_off_t pos) { IO_CACHE_SHARE *cshare= cache->share; DBUG_ENTER("lock_io_cache"); /* Enter the lock. */ mysql_mutex_lock(&cshare->mutex); cshare->running_threads--; DBUG_PRINT("io_cache_share", ("%s: 0x%lx pos: %lu running: %u", (cache == cshare->source_cache) ? "writer" : "reader", (long) cache, (ulong) pos, cshare->running_threads)); if (cshare->source_cache) { /* A write cache is synchronized to the read caches. */ if (cache == cshare->source_cache) { /* The writer waits until all readers are here. */ while (cshare->running_threads) { DBUG_PRINT("io_cache_share", ("writer waits in lock")); mysql_cond_wait(&cshare->cond_writer, &cshare->mutex); } DBUG_PRINT("io_cache_share", ("writer awoke, going to copy")); /* Stay locked. Leave the lock later by unlock_io_cache(). */ DBUG_RETURN(1); } /* The last thread wakes the writer. */ if (!cshare->running_threads) { DBUG_PRINT("io_cache_share", ("waking writer")); mysql_cond_signal(&cshare->cond_writer); } /* Readers wait until the data is copied from the writer. Another reason to stop waiting is the removal of the write thread. If this happens, we leave the lock with old data in the buffer. */ while ((!cshare->read_end || (cshare->pos_in_file < pos)) && cshare->source_cache) { DBUG_PRINT("io_cache_share", ("reader waits in lock")); mysql_cond_wait(&cshare->cond, &cshare->mutex); } /* If the writer was removed from the share while this thread was asleep, we need to simulate an EOF condition. The writer cannot reset the share variables as they might still be in use by readers of the last block. When we awake here then because the last joining thread signalled us. If the writer is not the last, it will not signal. So it is safe to clear the buffer here. */ if (!cshare->read_end || (cshare->pos_in_file < pos)) { DBUG_PRINT("io_cache_share", ("reader found writer removed. EOF")); cshare->read_end= cshare->buffer; /* Empty buffer. */ cshare->error= 0; /* EOF is not an error. */ } } else { /* There are read caches only. The last thread arriving in lock_io_cache() continues with a locked cache and reads the block. */ if (!cshare->running_threads) { DBUG_PRINT("io_cache_share", ("last thread joined, going to read")); /* Stay locked. Leave the lock later by unlock_io_cache(). */ DBUG_RETURN(1); } /* All other threads wait until the requested block is read by the last thread arriving. Another reason to stop waiting is the removal of a thread. If this leads to all threads being in the lock, we have to continue also. The first of the awaken threads will then do the read. */ while ((!cshare->read_end || (cshare->pos_in_file < pos)) && cshare->running_threads) { DBUG_PRINT("io_cache_share", ("reader waits in lock")); mysql_cond_wait(&cshare->cond, &cshare->mutex); } /* If the block is not yet read, continue with a locked cache and read. */ if (!cshare->read_end || (cshare->pos_in_file < pos)) { DBUG_PRINT("io_cache_share", ("reader awoke, going to read")); /* Stay locked. Leave the lock later by unlock_io_cache(). */ DBUG_RETURN(1); } /* Another thread did read the block already. */ } DBUG_PRINT("io_cache_share", ("reader awoke, going to process %u bytes", (uint) (cshare->read_end ? (size_t) (cshare->read_end - cshare->buffer) : 0))); /* Leave the lock. Do not call unlock_io_cache() later. The thread that filled the buffer did this and marked all threads as running. */ mysql_mutex_unlock(&cshare->mutex); DBUG_RETURN(0); } /* Unlock IO cache. SYNOPSIS unlock_io_cache() cache The cache of the thread leaving the lock. NOTE This is called by the thread that filled the buffer. It marks all threads as running and awakes them. This must not be done by any other thread. Do not signal cond_writer. Either there is no writer or the writer is the only one who can call this function. The reason for resetting running_threads to total_threads before waking all other threads is that it could be possible that this thread is so fast with processing the buffer that it enters the lock before even one other thread has left it. If every awoken thread would increase running_threads by one, this thread could think that he is again the last to join and would not wait for the other threads to process the data. RETURN void */ static void unlock_io_cache(IO_CACHE *cache) { IO_CACHE_SHARE *cshare= cache->share; DBUG_ENTER("unlock_io_cache"); DBUG_PRINT("io_cache_share", ("%s: 0x%lx pos: %lu running: %u", (cache == cshare->source_cache) ? "writer" : "reader", (long) cache, (ulong) cshare->pos_in_file, cshare->total_threads)); cshare->running_threads= cshare->total_threads; mysql_cond_broadcast(&cshare->cond); mysql_mutex_unlock(&cshare->mutex); DBUG_VOID_RETURN; } /* Read from IO_CACHE when it is shared between several threads. SYNOPSIS _my_b_read_r() cache IO_CACHE pointer Buffer Buffer to retrieve count bytes from file Count Number of bytes to read into Buffer NOTE This function is only called from the my_b_read() macro when there isn't enough characters in the buffer to satisfy the request. IMPLEMENTATION It works as follows: when a thread tries to read from a file (that is, after using all the data from the (shared) buffer), it just hangs on lock_io_cache(), waiting for other threads. When the very last thread attempts a read, lock_io_cache() returns 1, the thread does actual IO and unlock_io_cache(), which signals all the waiting threads that data is in the buffer. WARNING When changing this function, be careful with handling file offsets (end-of_file, pos_in_file). Do not cast them to possibly smaller types than my_off_t unless you can be sure that their value fits. Same applies to differences of file offsets. (Bug #11527) When changing this function, check _my_b_read(). It might need the same change. RETURN 0 we succeeded in reading all data 1 Error: can't read requested characters */ int _my_b_read_r(IO_CACHE *cache, uchar *Buffer, size_t Count) { my_off_t pos_in_file; size_t length, diff_length, left_length; IO_CACHE_SHARE *cshare= cache->share; DBUG_ENTER("_my_b_read_r"); if ((left_length= (size_t) (cache->read_end - cache->read_pos))) { DBUG_ASSERT(Count >= left_length); /* User is not using my_b_read() */ memcpy(Buffer, cache->read_pos, left_length); Buffer+= left_length; Count-= left_length; } while (Count) { size_t cnt, len; pos_in_file= cache->pos_in_file + (cache->read_end - cache->buffer); diff_length= (size_t) (pos_in_file & (IO_SIZE-1)); length=IO_ROUND_UP(Count+diff_length)-diff_length; length= ((length <= cache->read_length) ? length + IO_ROUND_DN(cache->read_length - length) : length - IO_ROUND_UP(length - cache->read_length)); if (cache->type != READ_FIFO && (length > (cache->end_of_file - pos_in_file))) length= (size_t) (cache->end_of_file - pos_in_file); if (length == 0) { cache->error= (int) left_length; DBUG_RETURN(1); } if (lock_io_cache(cache, pos_in_file)) { /* With a synchronized write/read cache we won't come here... */ DBUG_ASSERT(!cshare->source_cache); /* ... unless the writer has gone before this thread entered the lock. Simulate EOF in this case. It can be distinguished by cache->file. */ if (cache->file < 0) len= 0; else { /* Whenever a function which operates on IO_CACHE flushes/writes some part of the IO_CACHE to disk it will set the property "seek_not_done" to indicate this to other functions operating on the IO_CACHE. */ if (cache->seek_not_done) { if (mysql_file_seek(cache->file, pos_in_file, MY_SEEK_SET, MYF(0)) == MY_FILEPOS_ERROR) { cache->error= -1; unlock_io_cache(cache); DBUG_RETURN(1); } } len= mysql_file_read(cache->file, cache->buffer, length, cache->myflags); } DBUG_PRINT("io_cache_share", ("read %lu bytes", (ulong) len)); cache->read_end= cache->buffer + (len == (size_t) -1 ? 0 : len); cache->error= (len == length ? 0 : (int) len); cache->pos_in_file= pos_in_file; /* Copy important values to the share. */ cshare->error= cache->error; cshare->read_end= cache->read_end; cshare->pos_in_file= pos_in_file; /* Mark all threads as running and wake them. */ unlock_io_cache(cache); } else { /* With a synchronized write/read cache readers always come here. Copy important values from the share. */ cache->error= cshare->error; cache->read_end= cshare->read_end; cache->pos_in_file= cshare->pos_in_file; len= ((cache->error == -1) ? (size_t) -1 : (size_t) (cache->read_end - cache->buffer)); } cache->read_pos= cache->buffer; cache->seek_not_done= 0; if (len == 0 || len == (size_t) -1) { DBUG_PRINT("io_cache_share", ("reader error. len %lu left %lu", (ulong) len, (ulong) left_length)); cache->error= (int) left_length; DBUG_RETURN(1); } cnt= (len > Count) ? Count : len; memcpy(Buffer, cache->read_pos, cnt); Count -= cnt; Buffer+= cnt; left_length+= cnt; cache->read_pos+= cnt; } DBUG_RETURN(0); } /* Copy data from write cache to read cache. SYNOPSIS copy_to_read_buffer() write_cache The write cache. write_buffer The source of data, mostly the cache buffer. write_length The number of bytes to copy. NOTE The write thread will wait for all read threads to join the cache lock. Then it copies the data over and wakes the read threads. RETURN void */ static void copy_to_read_buffer(IO_CACHE *write_cache, const uchar *write_buffer, size_t write_length) { IO_CACHE_SHARE *cshare= write_cache->share; DBUG_ASSERT(cshare->source_cache == write_cache); /* write_length is usually less or equal to buffer_length. It can be bigger if _my_b_write() is called with a big length. */ while (write_length) { size_t copy_length= MY_MIN(write_length, write_cache->buffer_length); int MY_ATTRIBUTE((unused)) rc; rc= lock_io_cache(write_cache, write_cache->pos_in_file); /* The writing thread does always have the lock when it awakes. */ DBUG_ASSERT(rc); memcpy(cshare->buffer, write_buffer, copy_length); cshare->error= 0; cshare->read_end= cshare->buffer + copy_length; cshare->pos_in_file= write_cache->pos_in_file; /* Mark all threads as running and wake them. */ unlock_io_cache(write_cache); write_buffer+= copy_length; write_length-= copy_length; } } /* Do sequential read from the SEQ_READ_APPEND cache. We do this in three stages: - first read from info->buffer - then if there are still data to read, try the file descriptor - afterwards, if there are still data to read, try append buffer RETURNS 0 Success 1 Failed to read */ int _my_b_seq_read(IO_CACHE *info, uchar *Buffer, size_t Count) { size_t length, diff_length, left_length, save_count, max_length; my_off_t pos_in_file; save_count=Count; /* first, read the regular buffer */ if ((left_length=(size_t) (info->read_end-info->read_pos))) { DBUG_ASSERT(Count > left_length); /* User is not using my_b_read() */ memcpy(Buffer,info->read_pos, left_length); Buffer+=left_length; Count-=left_length; } lock_append_buffer(info); /* pos_in_file always point on where info->buffer was read */ if ((pos_in_file=info->pos_in_file + (size_t) (info->read_end - info->buffer)) >= info->end_of_file) goto read_append_buffer; /* With read-append cache we must always do a seek before we read, because the write could have moved the file pointer astray */ if (mysql_file_seek(info->file, pos_in_file, MY_SEEK_SET, MYF(0)) == MY_FILEPOS_ERROR) { info->error= -1; unlock_append_buffer(info); return (1); } info->seek_not_done=0; diff_length= (size_t) (pos_in_file & (IO_SIZE-1)); /* now the second stage begins - read from file descriptor */ if (Count >= (size_t) (IO_SIZE+(IO_SIZE-diff_length))) { /* Fill first intern buffer */ size_t read_length; length=(Count & (size_t) ~(IO_SIZE-1))-diff_length; if ((read_length= mysql_file_read(info->file,Buffer, length, info->myflags)) == (size_t) -1) { info->error= -1; unlock_append_buffer(info); return 1; } Count-=read_length; Buffer+=read_length; pos_in_file+=read_length; if (read_length != length) { /* We only got part of data; Read the rest of the data from the write buffer */ goto read_append_buffer; } left_length+=length; diff_length=0; } max_length= info->read_length-diff_length; if (max_length > (info->end_of_file - pos_in_file)) max_length= (size_t) (info->end_of_file - pos_in_file); if (!max_length) { if (Count) goto read_append_buffer; length=0; /* Didn't read any more chars */ } else { length= mysql_file_read(info->file,info->buffer, max_length, info->myflags); if (length == (size_t) -1) { info->error= -1; unlock_append_buffer(info); return 1; } if (length < Count) { memcpy(Buffer, info->buffer, length); Count -= length; Buffer += length; /* added the line below to make DBUG_ASSERT(pos_in_file==info->end_of_file) pass. otherwise this does not appear to be needed */ pos_in_file += length; goto read_append_buffer; } } unlock_append_buffer(info); info->read_pos=info->buffer+Count; info->read_end=info->buffer+length; info->pos_in_file=pos_in_file; memcpy(Buffer,info->buffer,(size_t) Count); return 0; read_append_buffer: /* Read data from the current write buffer. Count should never be == 0 here (The code will work even if count is 0) */ { /* First copy the data to Count */ size_t len_in_buff = (size_t) (info->write_pos - info->append_read_pos); size_t copy_len; size_t transfer_len; DBUG_ASSERT(info->append_read_pos <= info->write_pos); /* TODO: figure out if the assert below is needed or correct. */ DBUG_ASSERT(pos_in_file == info->end_of_file); copy_len= MY_MIN(Count, len_in_buff); memcpy(Buffer, info->append_read_pos, copy_len); info->append_read_pos += copy_len; Count -= copy_len; if (Count) info->error = (int)(save_count - Count); /* Fill read buffer with data from write buffer */ memcpy(info->buffer, info->append_read_pos, (size_t) (transfer_len=len_in_buff - copy_len)); info->read_pos= info->buffer; info->read_end= info->buffer+transfer_len; info->append_read_pos=info->write_pos; info->pos_in_file=pos_in_file+copy_len; info->end_of_file+=len_in_buff; } unlock_append_buffer(info); return Count ? 1 : 0; } /* Read one byte when buffer is empty */ int _my_b_get(IO_CACHE *info) { uchar buff; IO_CACHE_CALLBACK pre_read,post_read; if ((pre_read = info->pre_read)) (*pre_read)(info); if ((*(info)->read_function)(info,&buff,1)) return my_b_EOF; if ((post_read = info->post_read)) (*post_read)(info); return (int) (uchar) buff; } /* Write a byte buffer to IO_CACHE and flush to disk if IO_CACHE is full. RETURN VALUE 1 On error on write 0 On success -1 On error; my_errno contains error code. */ int _my_b_write(IO_CACHE *info, const uchar *Buffer, size_t Count) { size_t rest_length,length; my_off_t pos_in_file= info->pos_in_file; DBUG_EXECUTE_IF("simulate_huge_load_data_file", { pos_in_file=(my_off_t)(5000000000ULL); }); if (pos_in_file+info->buffer_length > info->end_of_file) { errno=EFBIG; set_my_errno(EFBIG); return info->error = -1; } rest_length= (size_t) (info->write_end - info->write_pos); memcpy(info->write_pos,Buffer,(size_t) rest_length); Buffer+=rest_length; Count-=rest_length; info->write_pos+=rest_length; if (my_b_flush_io_cache(info,1)) return 1; if (Count >= IO_SIZE) { /* Fill first intern buffer */ length=Count & (size_t) ~(IO_SIZE-1); if (info->seek_not_done) { /* Whenever a function which operates on IO_CACHE flushes/writes some part of the IO_CACHE to disk it will set the property "seek_not_done" to indicate this to other functions operating on the IO_CACHE. */ if (mysql_file_seek(info->file, info->pos_in_file, MY_SEEK_SET, MYF(0))) { info->error= -1; return (1); } info->seek_not_done=0; } if (mysql_file_write(info->file, Buffer, length, info->myflags | MY_NABP)) return info->error= -1; /* In case of a shared I/O cache with a writer we normally do direct write cache to read cache copy. Simulate this here by direct caller buffer to read cache copy. Do it after the write so that the cache readers actions on the flushed part can go in parallel with the write of the extra stuff. copy_to_read_buffer() synchronizes writer and readers so that after this call the readers can act on the extra stuff while the writer can go ahead and prepare the next output. copy_to_read_buffer() relies on info->pos_in_file. */ if (info->share) copy_to_read_buffer(info, Buffer, length); Count-=length; Buffer+=length; info->pos_in_file+=length; } memcpy(info->write_pos,Buffer,(size_t) Count); info->write_pos+=Count; return 0; } /* Append a block to the write buffer. This is done with the buffer locked to ensure that we don't read from the write buffer before we are ready with it. */ int my_b_append(IO_CACHE *info, const uchar *Buffer, size_t Count) { size_t rest_length,length; /* Assert that we cannot come here with a shared cache. If we do one day, we might need to add a call to copy_to_read_buffer(). */ DBUG_ASSERT(!info->share); lock_append_buffer(info); rest_length= (size_t) (info->write_end - info->write_pos); if (Count <= rest_length) goto end; memcpy(info->write_pos, Buffer, rest_length); Buffer+=rest_length; Count-=rest_length; info->write_pos+=rest_length; if (my_b_flush_io_cache(info,0)) { unlock_append_buffer(info); return 1; } if (Count >= IO_SIZE) { /* Fill first intern buffer */ length=Count & (size_t) ~(IO_SIZE-1); if (mysql_file_write(info->file,Buffer, length, info->myflags | MY_NABP)) { unlock_append_buffer(info); return info->error= -1; } Count-=length; Buffer+=length; info->end_of_file+=length; } end: memcpy(info->write_pos,Buffer,(size_t) Count); info->write_pos+=Count; unlock_append_buffer(info); return 0; } int my_b_safe_write(IO_CACHE *info, const uchar *Buffer, size_t Count) { /* Sasha: We are not writing this with the ? operator to avoid hitting a possible compiler bug. At least gcc 2.95 cannot deal with several layers of ternary operators that evaluated comma(,) operator expressions inside - I do have a test case if somebody wants it */ if (info->type == SEQ_READ_APPEND) return my_b_append(info, Buffer, Count); return my_b_write(info, Buffer, Count); } /* Write a block to disk where part of the data may be inside the record buffer. As all write calls to the data goes through the cache, we will never get a seek over the end of the buffer */ int my_block_write(IO_CACHE *info, const uchar *Buffer, size_t Count, my_off_t pos) { size_t length; int error=0; /* Assert that we cannot come here with a shared cache. If we do one day, we might need to add a call to copy_to_read_buffer(). */ DBUG_ASSERT(!info->share); if (pos < info->pos_in_file) { /* Of no overlap, write everything without buffering */ if (pos + Count <= info->pos_in_file) return (int)mysql_file_pwrite(info->file, Buffer, Count, pos, info->myflags | MY_NABP); /* Write the part of the block that is before buffer */ length= (uint) (info->pos_in_file - pos); if (mysql_file_pwrite(info->file, Buffer, length, pos, info->myflags | MY_NABP)) info->error= error= -1; Buffer+=length; pos+= length; Count-= length; #ifdef _WIN32 info->seek_not_done=1; #endif } /* Check if we want to write inside the used part of the buffer.*/ length= (size_t) (info->write_end - info->buffer); if (pos < info->pos_in_file + length) { size_t offset= (size_t) (pos - info->pos_in_file); length-=offset; if (length > Count) length=Count; memcpy(info->buffer+offset, Buffer, length); Buffer+=length; Count-= length; /* Fix length of buffer if the new data was larger */ if (info->buffer+length > info->write_pos) info->write_pos=info->buffer+length; if (!Count) return (error); } /* Write at the end of the current buffer; This is the normal case */ if (_my_b_write(info, Buffer, Count)) error= -1; return error; } /* Flush write cache */ #define LOCK_APPEND_BUFFER if (need_append_buffer_lock) \ lock_append_buffer(info); #define UNLOCK_APPEND_BUFFER if (need_append_buffer_lock) \ unlock_append_buffer(info); int my_b_flush_io_cache(IO_CACHE *info, int need_append_buffer_lock MY_ATTRIBUTE((unused))) { size_t length; my_off_t pos_in_file; my_bool append_cache= (info->type == SEQ_READ_APPEND); DBUG_ENTER("my_b_flush_io_cache"); DBUG_PRINT("enter", ("cache: 0x%lx", (long) info)); DBUG_EXECUTE_IF("simulate_error_during_flush_cache_to_file", { DBUG_RETURN(TRUE); }); if (!append_cache) need_append_buffer_lock= 0; if (info->type == WRITE_CACHE || append_cache) { if (info->file == -1) { if (real_open_cached_file(info)) DBUG_RETURN((info->error= -1)); } LOCK_APPEND_BUFFER; if ((length=(size_t) (info->write_pos - info->write_buffer))) { /* In case of a shared I/O cache with a writer we do direct write cache to read cache copy. Do it before the write here so that the readers can work in parallel with the write. copy_to_read_buffer() relies on info->pos_in_file. */ if (info->share) copy_to_read_buffer(info, info->write_buffer, length); pos_in_file=info->pos_in_file; /* If we have append cache, we always open the file with O_APPEND which moves the pos to EOF automatically on every write */ if (!append_cache && info->seek_not_done) { /* File touched, do seek */ if (mysql_file_seek(info->file, pos_in_file, MY_SEEK_SET, MYF(0)) == MY_FILEPOS_ERROR) { UNLOCK_APPEND_BUFFER; DBUG_RETURN((info->error= -1)); } if (!append_cache) info->seek_not_done=0; } if (!append_cache) info->pos_in_file+=length; info->write_end= (info->write_buffer+info->buffer_length- ((pos_in_file+length) & (IO_SIZE-1))); if (mysql_file_write(info->file,info->write_buffer,length, info->myflags | MY_NABP)) info->error= -1; else info->error= 0; if (!append_cache) { set_if_bigger(info->end_of_file,(pos_in_file+length)); } else { info->end_of_file+=(info->write_pos-info->append_read_pos); DBUG_ASSERT(info->end_of_file == mysql_file_tell(info->file, MYF(0))); } info->append_read_pos=info->write_pos=info->write_buffer; ++info->disk_writes; UNLOCK_APPEND_BUFFER; DBUG_RETURN(info->error); } } UNLOCK_APPEND_BUFFER; DBUG_RETURN(0); } /* Free an IO_CACHE object SYNOPSOS end_io_cache() info IO_CACHE Handle to free NOTES It's currently safe to call this if one has called init_io_cache() on the 'info' object, even if init_io_cache() failed. This function is also safe to call twice with the same handle. RETURN 0 ok # Error */ int end_io_cache(IO_CACHE *info) { int error=0; IO_CACHE_CALLBACK pre_close; DBUG_ENTER("end_io_cache"); DBUG_PRINT("enter",("cache: 0x%lx", (ulong) info)); /* Every thread must call remove_io_thread(). The last one destroys the share elements. */ DBUG_ASSERT(!info->share || !info->share->total_threads); if ((pre_close=info->pre_close)) { (*pre_close)(info); info->pre_close= 0; } if (info->alloced_buffer) { info->alloced_buffer=0; if (info->file != -1) /* File doesn't exist */ error= my_b_flush_io_cache(info,1); my_free(info->buffer); info->buffer=info->read_pos=(uchar*) 0; } if (info->type == SEQ_READ_APPEND) { /* Destroy allocated mutex */ info->type= TYPE_NOT_SET; mysql_mutex_destroy(&info->append_buffer_lock); } DBUG_RETURN(error); } /* end_io_cache */ /********************************************************************** Testing of MF_IOCACHE **********************************************************************/ #ifdef MAIN #include void die(const char* fmt, ...) { va_list va_args; va_start(va_args,fmt); fprintf(stderr,"Error:"); vfprintf(stderr, fmt,va_args); fprintf(stderr,", errno=%d\n", errno); exit(1); } int open_file(const char* fname, IO_CACHE* info, int cache_size) { int fd; if ((fd=my_open(fname,O_CREAT | O_RDWR,MYF(MY_WME))) < 0) die("Could not open %s", fname); if (init_io_cache(info, fd, cache_size, SEQ_READ_APPEND, 0,0,MYF(MY_WME))) die("failed in init_io_cache()"); return fd; } void close_file(IO_CACHE* info) { end_io_cache(info); my_close(info->file, MYF(MY_WME)); } int main(int argc, char** argv) { IO_CACHE sra_cache; /* SEQ_READ_APPEND */ MY_STAT status; const char* fname="/tmp/iocache.test"; int cache_size=16384; char llstr_buf[22]; int max_block,total_bytes=0; int i,num_loops=100,error=0; char *p; char* block, *block_end; MY_INIT(argv[0]); max_block = cache_size*3; if (!(block=(char*)my_malloc(PSI_NOT_INSTRUMENTED, max_block,MYF(MY_WME)))) die("Not enough memory to allocate test block"); block_end = block + max_block; for (p = block,i=0; p < block_end;i++) { *p++ = (char)i; } if (my_stat(fname,&status, MYF(0)) && my_delete(fname,MYF(MY_WME))) { die("Delete of %s failed, aborting", fname); } open_file(fname,&sra_cache, cache_size); for (i = 0; i < num_loops; i++) { char buf[4]; int block_size = abs(rand() % max_block); int4store(buf, block_size); if (my_b_append(&sra_cache,buf,4) || my_b_append(&sra_cache, block, block_size)) die("write failed"); total_bytes += 4+block_size; } close_file(&sra_cache); my_free(block); if (!my_stat(fname,&status,MYF(MY_WME))) die("%s failed to stat, but I had just closed it,\ wonder how that happened"); printf("Final size of %s is %s, wrote %d bytes\n",fname, llstr(status.st_size,llstr_buf), total_bytes); my_delete(fname, MYF(MY_WME)); /* check correctness of tests */ if (total_bytes != status.st_size) { fprintf(stderr,"Not the same number of bytes acutally in file as bytes \ supposedly written\n"); error=1; } exit(error); return 0; } #endif