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epoll: epoll_wait() should not use timespec_add_ns()

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commit 95aac7b1cd ("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.

[akpm@linux-foundation.org: s/epoll_set_mstimeout/ep_set_mstimeout/, per Davide]
Reported-by: Simon Kirby <sim@hostway.ca>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Shawn Bohrer <shawn.bohrer@gmail.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: <stable@kernel.org>		[2.6.37.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric Dumazet 2011-02-01 15:52:35 -08:00 committed by Linus Torvalds
parent 48db54ee2f
commit 0781b909b5
1 changed files with 13 additions and 3 deletions
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16
fs/eventpoll.c
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@ -1114,6 +1114,17 @@ static int ep_send_events(struct eventpoll *ep,
return ep_scan_ready_list(ep, ep_send_events_proc, &esed);
}
static inline struct timespec ep_set_mstimeout(long ms)
{
struct timespec now, ts = {
.tv_sec = ms / MSEC_PER_SEC,
.tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC),
};
ktime_get_ts(&now);
return timespec_add_safe(now, ts);
}
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
int maxevents, long timeout)
{
@ -1121,12 +1132,11 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
unsigned long flags;
long slack;
wait_queue_t wait;
struct timespec end_time;
ktime_t expires, *to = NULL;
if (timeout > 0) {
ktime_get_ts(&end_time);
timespec_add_ns(&end_time, (u64)timeout * NSEC_PER_MSEC);
struct timespec end_time = ep_set_mstimeout(timeout);
slack = select_estimate_accuracy(&end_time);
to = &expires;
*to = timespec_to_ktime(end_time);