linux-kernel - Re: [PATCH v0 27/71] perf evlist: Add 'system

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:	Thu, 12 Dec 2013 14:22:10 +0200
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	David Ahern <dsahern@...il.com>
CC:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v0 27/71] perf evlist: Add 'system_wide' option

On 11/12/13 21:37, David Ahern wrote:
> On 12/11/13, 5:36 AM, Alexander Shishkin wrote:
>> From: Adrian Hunter <adrian.hunter@...el.com>
>>
>> Add an option to cause a selected event
>> to be opened always without a pid when
>> configured by perf_evsel__config().
>>
>> This is needed when using the sched_switch
>> tracepoint to follow object code execution.
>> sched_switch occurs before the task
>> switch and so it cannot record it in a
>> context limited to that task.  Note
>> that also means that sched_switch is
>> useless when capturing data per-thread,
>> as is the 'context-switches' software
>> event for the same reason.
> 
> This seems like a tailored solution for what is really a generic problem:
> you need events to have different attributes -- a mix of system wide, task
> based, with or without callchains and other sample options.

Actually in this case it is not the attribute but another parameter of the
perf_event_open syscall, namely the pid.  The effect of that is that there
are potentially fewer file descriptors needed for that event i.e. just 1 per
cpu compared with 1 per cpu per thread.

This is a generic solution for the case where you want to mix an event that
is not tied to a process, with other events that are.

If it were the attribute it would be easy because 'attr' is a member of
'struct evsel' so it can simply be changed directly.

--
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/