linux-kernel - Re: [PATCH v10 04/11] sched: Make sched entity usage tracking scale-invariant

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, 03 Mar 2015 12:51:27 +0000
From:	Dietmar Eggemann <dietmar.eggemann@....com>
To:	Vincent Guittot <vincent.guittot@...aro.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	"kamalesh@...ux.vnet.ibm.com" <kamalesh@...ux.vnet.ibm.com>
CC:	"riel@...hat.com" <riel@...hat.com>,
	"efault@....de" <efault@....de>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Paul Turner <pjt@...gle.com>, Ben Segall <bsegall@...gle.com>
Subject: Re: [PATCH v10 04/11] sched: Make sched entity usage tracking scale-invariant

On 27/02/15 15:54, Vincent Guittot wrote:
> From: Morten Rasmussen <morten.rasmussen@....com>
> 
> Apply frequency scale-invariance correction factor to usage tracking.
> Each segment of the running_load_avg geometric series is now scaled by the

The same comment I sent out on [PATCH v10 07/11]:

The use of underscores in running_load_avg implies to me that this is a
data member of struct sched_avg or something similar. But there is no
running_load_avg in the current code. However, I can see that
sched_avg::*running_avg_sum* (and therefore
cfs_rq::*utilization_load_avg*) are frequency scale invariant.

-- Dietmar

> current frequency so the utilization_avg_contrib of each entity will be
> invariant with frequency scaling. As a result, utilization_load_avg which is
> the sum of utilization_avg_contrib, becomes invariant too. So the usage level
> that is returned by get_cpu_usage, stays relative to the max frequency as the
> cpu_capacity which is is compared against.
> Then, we want the keep the load tracking values in a 32bits type, which implies
> that the max value of {runnable|running}_avg_sum must be lower than
> 2^32/88761=48388 (88761 is the max weigth of a task). As LOAD_AVG_MAX = 47742,
> arch_scale_freq_capacity must return a value less than
> (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY = 1024).
> So we define the range to [0..SCHED_SCALE_CAPACITY] in order to avoid overflow.


--
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/