The patch titled
epoll: epoll_wait() should not use timespec_add_ns()
has been added to the -mm tree. Its filename is
epoll-epoll_wait-should-not-use-timespec_add_ns.patch
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------------------------------------------------------
Subject: epoll: epoll_wait() should not use timespec_add_ns()
From: Eric Dumazet <[email protected]>
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.
Reported-by: Simon Kirby <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Cc: Shawn Bohrer <[email protected]>
Cc: Davide Libenzi <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: <[email protected]> [2.6.37.x]
Signed-off-by: Andrew Morton <[email protected]>
---
fs/eventpoll.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff -puN fs/eventpoll.c~epoll-epoll_wait-should-not-use-timespec_add_ns
fs/eventpoll.c
--- a/fs/eventpoll.c~epoll-epoll_wait-should-not-use-timespec_add_ns
+++ a/fs/eventpoll.c
@@ -1114,6 +1114,17 @@ static int ep_send_events(struct eventpo
return ep_scan_ready_list(ep, ep_send_events_proc, &esed);
}
+static inline struct timespec epoll_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,
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 = epoll_set_mstimeout(timeout);
+
slack = select_estimate_accuracy(&end_time);
to = &expires;
*to = timespec_to_ktime(end_time);
_
Patches currently in -mm which might be from [email protected] are
origin.patch
epoll-epoll_wait-should-not-use-timespec_add_ns.patch
mm-numa-aware-alloc_task_struct_node.patch
mm-numa-aware-alloc_thread_info_node.patch
kthread-numa-aware-kthread_create_on_cpu.patch
kthread-use-kthread_create_on_cpu.patch
net-convert-%p-usage-to-%pk.patch
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