linux-kernel - Re: [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in scale_rt

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]

Message-ID: <566ED47D.6030504@unitn.it>
Date:	Mon, 14 Dec 2015 15:38:53 +0100
From:	Luca Abeni <luca.abeni@...tn.it>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	Steve Muckle <steve.muckle@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>,
	Michael Turquette <mturquette@...libre.com>
Subject: Re: [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in
 scale_rt_capacity

On 12/14/2015 03:02 PM, Vincent Guittot wrote:
[...]
>>>> Small nit: why "average" utilization? I think a better name would be
>>>> "runqueue utilization"
>>>> or "local utilization", or something similar... If I understand correctly
>>>> (sorry if I
>>>> missed something), this is not an average, but the sum of the
>>>> utilisations
>>>> of the tasks
>>>> on this runqueue... No?
>>>
>>>
>>> I have used "average" because it doesn't reflect the active/actual
>>> utilization of the run-queue but the forecasted average bandwidth of
>>> the CPU that will be used by deadline task.
>>
>> Well, this is just nitpicking, so feel free to ignore (I just mentioned
>> this point because I was initially confused by the "average" name). But I
>> think this is "maximum", or "worst-case", not "average", because (as far
>> as I can understand) this field indicates that SCHED_DEADLINE tasks will
>> not be able to consume more than this fraction of CPU (if they try to
>> consume more, the scheduler throttles them).
>>
>>> I'm open to change the name if another one makes more sense
>>
>> In real-time literature this is often called simply "utilization" (or
>> "worst-case
>> utilization" by someone): when a task can have a variable execution time,
>> its
>> utilization is defined as WCET (maximum execution time) / period.
>
> ok. Let follow real-time literature wording and remove "average" to
> keep only utilization.
> so the variable will be named:
>
> s64 util_bw;
Well, "utilization" and "bandwidth" are often used to indicate the same
quantity, so "util_bw" sounds strange. I'd call it simply "utilization" or
"bandwidth" (otherwise, just leave the name as it is... I said this is just
nitpicking).



				Luca
--
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/