From: theoleblond <theodore.leblond@xxxxxxxxx> Date: Wed, 16 May 2012 06:52:49 -0700 I played around with this quite a bit. After trying some more complex schemes, I found that what worked best is to just sleep 1 millisecond between iterations. Though it's a very short time, it still completely eliminates the busy wait condition, without hurting perf. There code uses SleepEx(1, TRUE) to sleep. See this page for a good discussion of why that is better than calling SwitchToThread, which is what was used previously: http://stackoverflow.com/questions/1383943/switchtothread-vs-sleep1 Note that calling SleepEx(0, TRUE) does *not* solve the busy wait. The most striking case was when testing on a UNC share with a large repo, on a single CPU machine. Without the fix, it took 4 minutes 15 seconds, and with the fix it took just 1:08! I think it's because git-upload-pack's busy wait was eating the CPU away from the git process that's doing the real work. With multi-proc, the timing is not much different, but tons of CPU time is still wasted, which can be a killer on a server that needs to do bunch of other things. I also tested the very fast local case, and didn't see any measurable difference. On a big repo with 4500 files, the upload-pack took about 2 seconds with and without the fix. --- This is one of the patches that lives in msysGit, could it be accepted upstream? It modifies the Windows compat function only. Have a nice day, Stepan compat/poll/poll.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/compat/poll/poll.c b/compat/poll/poll.c index 31163f2..c5a9a93 100644 --- a/compat/poll/poll.c +++ b/compat/poll/poll.c @@ -605,7 +605,9 @@ restart: if (!rc && timeout == INFTIM) { - SwitchToThread(); + /* Sleep 1 millisecond to avoid busy wait */ + SleepEx(1, TRUE); + goto restart; } -- 1.9.2.msysgit.0.158.g6070cee -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html