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2014-04-29compat/poll: sleep 1 millisecond to avoid busy waitLibravatar Theodore Leblond1-1/+1
SwitchToThread() only gives away the rest of the current time slice to another thread in the current process. So if the thread that feeds the file decscriptor we're polling is not in the current process, we get busy-waiting. 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. [jc: this was first accepted in msysgit tree in May 2012 via a pull request and Paolo Bonzini has also accepted the same fix to Gnulib around the same time; see $gmane/247518 for a bit more detail] Signed-off-by: Stepan Kasal <kasal@ucw.cz> Acked-by: Johannes Sixt <j6t@kdbg.org> Acked-by: Erik Faye-Lund <kusmabite@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-09-11Windows: do not redefine _WIN32_WINNTLibravatar Sebastian Schuberth1-1/+1
With MinGW runtime version 4.0 this interferes with the previous definition from sdkddkver.h. Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-04-28compat/poll/poll.c: Fix a sparse warningLibravatar Ramsay Jones1-1/+1
Sparse issues an 'Using plain integer as NULL pointer' warning when passing the constant '0' as the second parameter in the call to the WSAEventSelect() function. The function parameter has a pointer type (WSAEVENT, aka HANDLE, aka void *) so that, in order to suppress the warning, we simply pass NULL for that parameter in the function call expression. Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-09-17make poll() work on platforms that can't recv() on a non-socketLibravatar Joachim Schmitz1-0/+4
This way it just got added to gnulib too the other day. Signed-off-by: Joachim Schmitz <jojo@schmitz-digital.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-09-17poll() exits too early with EFAULT if 1st arg is NULLLibravatar Joachim Schmitz1-1/+1
If poll() is used as a milli-second sleep, like in help.c, by passing a NULL in the 1st and a 0 in the 2nd arg, it exits with EFAULT. As per Paolo Bonzini, the original author, this is a bug and to be fixed Like in this commit, which is not to exit if the 2nd arg is 0. It got fixed In gnulib in the same manner the other day. Signed-off-by: Joachim Schmitz <jojo@schmitz-digital.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-09-17fix some win32 specific dependencies in poll.cLibravatar Joachim Schmitz1-2/+6
In order for non-win32 platforms to be able to use poll.c, #ifdef the inclusion of two header files properly Signed-off-by: Joachim Schmitz <jojo@schmitz-digital.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-09-17make poll available for other platforms lacking itLibravatar Joachim Schmitz1-0/+606
move poll.[ch] out of compat/win32/ into compat/poll/ and adjust Makefile with the changed paths. Adding comments to Makefile about how/when to enable it and add logic for this Signed-off-by: Joachim Schmitz <jojo@schmitz-digital.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>