linux-kernel - Re: [PATCH v10 6/7] sched: Provide runnable_load_avg back to cfs

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:	Tue, 21 Jul 2015 08:44:01 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Boqun Feng <boqun.feng@...il.com>
Cc:	mingo@...nel.org, peterz@...radead.org,
	linux-kernel@...r.kernel.org, pjt@...gle.com, bsegall@...gle.com,
	morten.rasmussen@....com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, umgwanakikbuti@...il.com,
	len.brown@...el.com, rafael.j.wysocki@...el.com,
	arjan@...ux.intel.com, fengguang.wu@...el.com
Subject: Re: [PATCH v10 6/7] sched: Provide runnable_load_avg back to cfs_rq

On Tue, Jul 21, 2015 at 09:08:07AM +0800, Boqun Feng wrote:
> Hi Yuyang,
> 
> On Wed, Jul 15, 2015 at 08:04:41AM +0800, Yuyang Du wrote:
> > The cfs_rq's load_avg is composed of runnable_load_avg and blocked_load_avg.
> > Before this series, sometimes the runnable_load_avg is used, and sometimes
> > the load_avg is used. Completely replacing all uses of runnable_load_avg
> > with load_avg may be too big a leap, i.e., the blocked_load_avg is concerned
> > to result in overrated load. Therefore, we get runnable_load_avg back.
> > 
> > The new cfs_rq's runnable_load_avg is improved to be updated with all of the
> > runnable sched_eneities at the same time, so the one sched_entity updated and
> > the others stale problem is solved.
> > 
> 
> How about tracking cfs_rq's blocked_load_avg instead of
> runnable_load_avg, because, AFAICS:
> 
> cfs_rq->runnable_load_avg = se->avg.load_avg - cfs_rq->blocked_load_avg.

No, cfs_rq->runnable_load_avg = cfs_rq->avg.load_avg - cfs_rq->blocked_load_avg,
without rounding errors and the like.
 
> se is the corresponding sched_entity of cfs_rq. And when we need the
> runnable_load_avg, we just calculate by the expression above.
> 
> This can be thought as a lazy way to update runnable_load_avg, and we
> don't need to modify __update_load_avg any more.

Not lazy at all, but adding (as of now) useless blocked_load_avg and an
extra subtraction.

Or did you forget blocked_load_avg also needs to be updated/decayed as
time elapses?
--
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/