Messages in this thread Patch in this message | | | Subject | Re: sys_epoll_wait high CPU load in 2.6.37 | From | Eric Dumazet <> | Date | Wed, 26 Jan 2011 17:13:29 +0100 |
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Le mercredi 26 janvier 2011 à 16:59 +0100, Eric Dumazet a écrit : > Le mercredi 26 janvier 2011 à 07:52 -0800, Davide Libenzi a écrit : > > > For "above", I meant the current epoll expire time calculation, which was > > described above in the message ;) > > Well, problem was not an overflow, but doing a loop 2.000.000 times ;) > > > The hint for a timespec_add_ms() was because we must be doing something > > similar in poll, don't we (/me got no code in front ATM)? > > Apparently its done differently in poll(), using > poll_select_set_timeout() helper. > > > Give me some minutes I'll try to cook an alternate patch >
Here is the alternate patch, using poll_select_set_timeout() helper
Thanks
[PATCH v2] epoll: epoll_wait() should not use timespec_add_ns()
commit 95aac7b1cd224f (epoll: make epoll_wait() use the hrtimer range feature) added a performance regression because it uses timespec_add_ns() with potential very large 'ns' values.
Use poll_select_set_timeout() helper like poll()/select()
Reported-by: Simon Kirby <sim@hostway.ca> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Shawn Bohrer <shawn.bohrer@gmail.com> CC: Davide Libenzi <davidel@xmailserver.org> CC: Thomas Gleixner <tglx@linutronix.de> CC: Andrew Morton <akpm@linux-foundation.org> --- fs/eventpoll.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index cc8a9b7..94d887b 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1125,8 +1125,8 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, ktime_t expires, *to = NULL; if (timeout > 0) { - ktime_get_ts(&end_time); - timespec_add_ns(&end_time, (u64)timeout * NSEC_PER_MSEC); + poll_select_set_timeout(&end_time, timeout / MSEC_PER_SEC, + NSEC_PER_MSEC * (timeout % MSEC_PER_SEC)); slack = select_estimate_accuracy(&end_time); to = &expires; *to = timespec_to_ktime(end_time);
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