Il 16/05/2012 21:16, Erik Faye-Lund ha scritto:
> From: theoleblond <theodore.lebl...@gmail.com>
>
> 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. This can lead
> to very poor performance in some cases, so we better just
> wait a tiny amount instead.
>
> * lib/poll.c: use SleepEx(1, TRUE) instead of SwitchToThread()
> ---
>
> Here's a patch we've applied to Git for Windows. Perhaps it's
> useful upstream as well?
>
> I'm forwarding it on behalf of Theodore, who was nice enough
> to debug a performance issue and nail down a fix. Thanks,
> Theodore!
>
> ChangeLog | 13 +++++++++++++
> lib/poll.c | 3 ++-
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/ChangeLog b/ChangeLog
> index aeb3cf8..b94c311 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,3 +1,16 @@
> +2012-05-16 theoleblond <theodore.lebl...@gmail.com>
> +
> + poll: prevent busy-waiting
> +
> + 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. This can lead
> + to very poor performance in some cases, so we better just
> + wait a tiny amount instead.
> +
> + * lib/poll.c: use SleepEx(1, TRUE) instead of SwitchToThread()
> +
> 2012-05-15 Pádraig Brady <p...@draigbrady.com>
>
> fsusage: fix block size returned on older Linux 2.6
> diff --git a/lib/poll.c b/lib/poll.c
> index 3071b12..235338e 100644
> --- a/lib/poll.c
> +++ b/lib/poll.c
> @@ -598,7 +598,8 @@ restart:
>
> if (!rc && timeout == INFTIM)
> {
> - SwitchToThread();
> + /* Sleep 1 millisecond to avoid busy wait */
> + SleepEx(1, TRUE);
> goto restart;
> }
>
Looks good, do you have commit access?
Paolo
