Date: Tue, 21 Jul 2015 09:08:07 +0800
From: Boqun Feng <boqun.feng@gmail.com>
To: Yuyang Du <yuyang.du@intel.com>
Cc: mingo@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org,
        pjt@google.com, bsegall@google.com, morten.rasmussen@arm.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        umgwanakikbuti@gmail.com, len.brown@intel.com,
        rafael.j.wysocki@intel.com, arjan@linux.intel.com,
        fengguang.wu@intel.com
Subject: Re: [PATCH v10 6/7] sched: Provide runnable_load_avg back to cfs_rq
Message-ID: <20150721010346.GA2882@fixme-laptop.cn.ibm.com>
References: <1436918682-4971-1-git-send-email-yuyang.du@intel.com>
 <1436918682-4971-7-git-send-email-yuyang.du@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1436918682-4971-7-git-send-email-yuyang.du@intel.com>
User-Agent: Mutt/1.5.23+102 (2ca89bed6448) (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1337
Lines: 32

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.

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.

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