From c3bb3da52c81abcde83cb72e90b1b61f0627f580 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 22 Jun 2023 11:16:21 +0200
Subject: Half Windows sleep times, use exponential backoff in fdselect()

---
 libbutl/fdstream.cxx   | 12 +++++++-----
 libbutl/filesystem.cxx | 10 +++++-----
 2 files changed, 12 insertions(+), 10 deletions(-)

(limited to 'libbutl')

diff --git a/libbutl/fdstream.cxx b/libbutl/fdstream.cxx
index 5a0c479..e29bb50 100644
--- a/libbutl/fdstream.cxx
+++ b/libbutl/fdstream.cxx
@@ -1164,12 +1164,12 @@ namespace butl
     // open it results in EINVAL POSIX error, ERROR_USER_MAPPED_FILE system
     // error. So we retry those as well.
     //
-    for (size_t i (0); i < 21; ++i)
+    for (size_t i (0); i < 41; ++i)
     {
-      // Sleep 100 milliseconds before the open retry.
+      // Sleep 50 milliseconds before the open retry.
       //
       if (i != 0)
-        Sleep (100);
+        Sleep (50);
 
       fd = pass_perm
            ? _sopen (f, of, _SH_DENYNO, pf)
@@ -1989,7 +1989,7 @@ namespace butl
     //
     size_t r (0);
 
-    while (true)
+    for (size_t i (0);; ++i)
     {
       for (fdselect_state& s: read)
       {
@@ -2062,7 +2062,9 @@ namespace butl
       if (r != 0)
         break;
 
-      DWORD t (50);
+      // Use exponential backoff but not too aggressive and with 25ms max.
+      //
+      DWORD t (i >= 100 ? 25 : 1 + (i / 4));
 
       if (timeout)
       {
diff --git a/libbutl/filesystem.cxx b/libbutl/filesystem.cxx
index 07d0590..28a0de8 100644
--- a/libbutl/filesystem.cxx
+++ b/libbutl/filesystem.cxx
@@ -1142,12 +1142,12 @@ namespace butl
     // failure (see mventry() for details). If that's the case, we will keep
     // trying to move the file for two seconds.
     //
-    for (size_t i (0); i < 21; ++i)
+    for (size_t i (0); i < 41; ++i)
     {
-      // Sleep 100 milliseconds before the removal retry.
+      // Sleep 50 milliseconds before the removal retry.
       //
       if (i != 0)
-        Sleep (100);
+        Sleep (50);
 
       ur = _unlink (f);
 
@@ -1792,12 +1792,12 @@ namespace butl
     // fdopen().
     //
     DWORD ec;
-    for (size_t i (0); i < 21; ++i)
+    for (size_t i (0); i < 41; ++i)
     {
       // Sleep 100 milliseconds before the move retry.
       //
       if (i != 0)
-        Sleep (100);
+        Sleep (50);
 
       if (MoveFileExA (f, t, mfl))
         return;
-- 
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