lkml.org 
[lkml]   [2018]   [Jul]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/2] fs/epoll: loosen irq safety in ep_scan_ready_list()
Date
Saving and restoring interrupts in ep_scan_ready_list() is an
overkill as it is never called with interrupts disabled. Loosen
this to simply disabling local irqs such that archs where managing
irqs is expensive or virtual environments. This patch yields
some throughput improvements on a workload that is epoll intensive
running on a single Xen DomU.

1 Job 7500 --> 8800 enq/s (+17%)
2 Jobs 14000 --> 15200 enq/s (+8%)
3 Jobs 20500 --> 22300 enq/s (+8%)
4 Jobs 25000 --> 28000 enq/s (+8-12)%

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
fs/eventpoll.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 2737ef591b3e..2247769eb941 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -667,7 +667,6 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep,
{
__poll_t res;
int pwake = 0;
- unsigned long flags;
struct epitem *epi, *nepi;
LIST_HEAD(txlist);

@@ -687,17 +686,17 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep,
* because we want the "sproc" callback to be able to do it
* in a lockless way.
*/
- spin_lock_irqsave(&ep->wq.lock, flags);
+ spin_lock_irq(&ep->wq.lock);
list_splice_init(&ep->rdllist, &txlist);
ep->ovflist = NULL;
- spin_unlock_irqrestore(&ep->wq.lock, flags);
+ spin_unlock_irq(&ep->wq.lock);

/*
* Now call the callback function.
*/
res = (*sproc)(ep, &txlist, priv);

- spin_lock_irqsave(&ep->wq.lock, flags);
+ spin_lock_irq(&ep->wq.lock);
/*
* During the time we spent inside the "sproc" callback, some
* other events might have been queued by the poll callback.
@@ -739,7 +738,7 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep,
if (waitqueue_active(&ep->poll_wait))
pwake++;
}
- spin_unlock_irqrestore(&ep->wq.lock, flags);
+ spin_unlock_irq(&ep->wq.lock);

if (!ep_locked)
mutex_unlock(&ep->mtx);
--
2.16.4
\
 
 \ /
  Last update: 2018-07-20 19:31    [W:0.082 / U:0.368 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site