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From: Davide Libenzi <davidel@xmailserver.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Shawn Bohrer <shawn.bohrer@gmail.com>,
	Simon Kirby <sim@hostway.ca>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: sys_epoll_wait high CPU load in 2.6.37
Date: Wed, 26 Jan 2011 10:06:28 -0800 (PST)	[thread overview]
Message-ID: <alpine.DEB.2.00.1101261001550.14705@localhost6.localdomain6> (raw)
In-Reply-To: <1296064311.2899.90.camel@edumazet-laptop>

On Wed, 26 Jan 2011, Eric Dumazet wrote:

> > > --- 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);
> > 
> > poll_select_set_timeout() jumps through some extra hoops that
> > aren't necessary in the epoll case so I actually like your previous
> > patch better.
> 
> Well, I dont care, I let Davide decide, he is the boss ;)
> 
> This is a stable candidate, so adding timespec_add_ms() sounds overkill.

Eric, if you look at fs/select.c (~line 925), poll does exactly the same 
thing as epoll do.
It too, ignores the eventual return value of poll_select_set_timeout(), so 
maybe a little bit more optimized ktime_get_ts+timespec_add_ms could make 
sense.


- Davide



  reply	other threads:[~2011-01-26 18:06 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-26  0:09 sys_epoll_wait high CPU load in 2.6.37 Simon Kirby
2011-01-26  7:18 ` Eric Dumazet
2011-01-26 11:16   ` Eric Dumazet
2011-01-26 15:31     ` Davide Libenzi
2011-01-26 15:43       ` Eric Dumazet
2011-01-26 15:52         ` Davide Libenzi
2011-01-26 15:59           ` Eric Dumazet
2011-01-26 16:13             ` Eric Dumazet
2011-01-26 17:20               ` Shawn Bohrer
2011-01-26 17:51                 ` Eric Dumazet
2011-01-26 18:06                   ` Davide Libenzi [this message]
2011-01-26 18:18                     ` Eric Dumazet
2011-01-26 18:45                       ` Eric Dumazet
2011-01-28  0:17                         ` Davide Libenzi

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