linux-kernel - Re: [RFC PATCH] perf: Add PERF_RECORD_SWITCH to indicate context switches

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: <557AECB4.5050709@gmail.com>
Date:	Fri, 12 Jun 2015 08:29:08 -0600
From:	David Ahern <dsahern@...il.com>
To:	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Andi Kleen <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	mathieu.poirier@...aro.org, Pawel Moll <pawel.moll@....com>
Subject: Re: [RFC PATCH] perf: Add PERF_RECORD_SWITCH to indicate context
 switches

On 6/12/15 5:12 AM, Adrian Hunter wrote:
>>> This new PERF_RECORD_SWITCH event does not have those problems
>>> and it also has a couple of other small advantages. It is
>>> easier to use because it is an auxiliary event (like mmap,
>>> comm and task events) which can be enabled by setting a single
>>> bit. It is smaller than sched:sched_switch and easier to parse.
>>
>> Right, so the one wee problem I have is that this only provides sched_in
>> data, I imagine people might be interested in sched_out as well.
>
> That is not a problem although it would be interesting to know the use-case.
> To me it seemed unreasonable to expect to analyze scheduler behaviour
> without admin-level privileges since it is inherently an administrative
> activity.

One use case is wanting to analyze a set of processes -- how long they 
run when scheduled, where they are when scheduled out, scheduling delay 
on wakeups, time between scehd in. I wrote the timehist tool in 2010 it 
has been really helpful understanding what is happening on each cpu and 
characteristics of a set of processes (e.g. ping ponging between tasks 
sending messages to each other).

In this case it is not necessarily scheduler behavior (though it does it 
enter the picture to a degree), but rather behavior of a process or set 
of tasks.
--
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/