From 0781b909b5586f4db720b5d1838b78f9d8e42f14 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 1 Feb 2011 15:52:35 -0800 Subject: [PATCH] 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. [akpm@linux-foundation.org: s/epoll_set_mstimeout/ep_set_mstimeout/, per Davide] Reported-by: Simon Kirby Signed-off-by: Eric Dumazet Cc: Shawn Bohrer Acked-by: Davide Libenzi Cc: [2.6.37.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/eventpoll.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index cc8a9b7d6064..267d0ada4541 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -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); -- 2.20.1