linux-kernel - Re: [PATCH] sched: Reduce the rate of needless idle load balancing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 21 May 2014 09:37:47 -0700
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Jason Low <jason.low2@...com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <len.brown@...el.com>, Russ Anderson <rja@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Hedi Berriche <hedi@....com>, Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: Reduce the rate of needless idle load balancing

On Tue, 2014-05-20 at 18:15 -0700, Joe Perches wrote:
> On Tue, 2014-05-20 at 14:04 -0700, Tim Chen wrote:
> > On Tue, 2014-05-20 at 13:59 -0700, Tim Chen wrote:
> > > On Tue, 2014-05-20 at 13:51 -0700, Jason Low wrote:
> > > > On Tue, May 20, 2014 at 1:17 PM, Tim Chen <tim.c.chen@...ux.intel.com> wrote:
> > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> []
> > > > If we want to do idle load balancing only when it is due for a
> > > > balance, shouldn't the above just be "if (time_after(jiffies,
> > > > rq->next_balance))"?
> > > 
> > > If rq->next_balance and jiffies are equal, then
> > > time_after(jiffies, rq->next_balance) check will be false and
> > > you will not do balance.  But actually you want to balance
> > > for this case so the jiffies+1 was used.
> > 
> > So maybe I should switch the check to 
> > if (time_before(rq->next_balance, jiffies))
> 
> time_after_eq() or time_is_after_eq_jiffies()
> 
> 

I prefer time_after_eq to keep the code style consistent with the
rest of the code in fair.c.

Tim

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/