From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>, Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, vince@deater.net,
eranian@google.com, Arnaldo Carvalho de Melo <acme@infradead.org>,
tglx@linutronix.de
Subject: Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation
Date: Mon, 26 Sep 2016 15:39:49 +0300 [thread overview]
Message-ID: <87y42erg16.fsf@ashishki-desk.ger.corp.intel.com> (raw)
In-Reply-To: <20160926090354.GK5012@twins.programming.kicks-ass.net>
Peter Zijlstra <peterz@infradead.org> writes:
> On Mon, Sep 26, 2016 at 11:27:08AM +0300, Alexander Shishkin wrote:
>> Peter Zijlstra <peterz@infradead.org> writes:
>> > At which point we _should_ start failing fork(), which is a somewhat
>> > unexpected, and undesirable side-effect.
>>
>> I'm not sure I see why we should fail fork() when we run out of pinned
>> memory.
>
> Well, we cannot fully honour the inherit, what other option do we have?
> Silently malfunctioning? That's far worse.
We can still put a note there saying that we tried. The user will know
to adjust their buffer size requirement or the RLIMIT_MEMLOCK.
>> > Ideally we'd unpin the old buffers and repin the new buffers on context
>> > switch, but that's impossible since faulting needs scheduling,
>> > recursion, we loose.
>>
>> Or we can have per-cpu buffers for all user's tasks, record where each
>> task starts and ends in each buffer and cut out only bits relevant to
>> the task(s) that dump core.
>
> Which gets you the problem that when a task dumps core there might not
> be any state in the buffer, because the previous task flushed it all out
> :/
Well, there's going to be at list something that leads up to the core
dump if this task is the last one to schedule in for this buffer. It's a
bit more gambling, though.
Regards,
--
Alex
next prev parent reply other threads:[~2016-09-26 12:40 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-23 11:27 [RFC PATCH 0/6] perf: Add AUX data sampling Alexander Shishkin
2016-09-23 11:27 ` [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation Alexander Shishkin
2016-09-23 12:14 ` Peter Zijlstra
2016-09-23 14:27 ` Alexander Shishkin
2016-09-23 15:27 ` Peter Zijlstra
2016-09-23 15:58 ` Alexander Shishkin
2016-09-23 17:26 ` Andi Kleen
2016-09-23 20:28 ` Peter Zijlstra
2016-09-26 8:27 ` Alexander Shishkin
2016-09-26 9:03 ` Peter Zijlstra
2016-09-26 12:39 ` Alexander Shishkin [this message]
2016-09-26 16:13 ` Alexander Shishkin
2016-09-23 11:27 ` [RFC PATCH 2/6] perf: Add api to (de-)allocate AUX buffers for kernel counters Alexander Shishkin
2016-09-23 11:27 ` [RFC PATCH 3/6] perf: Add a helper for looking up pmus by type Alexander Shishkin
2016-09-23 11:27 ` [RFC PATCH 4/6] perf: Add infrastructure for using AUX data in perf samples Alexander Shishkin
2016-09-23 11:27 ` [RFC PATCH 5/6] perf: Disable PMU around address filter adjustment Alexander Shishkin
2016-09-23 11:27 ` [RFC PATCH 6/6] perf: Disable IRQs in address filter sync path Alexander Shishkin
2016-09-26 16:18 ` Alexander Shishkin
2016-10-04 16:49 ` Mathieu Poirier
2016-09-23 11:49 ` [RFC PATCH 0/6] perf: Add AUX data sampling Peter Zijlstra
2016-09-23 17:19 ` Andi Kleen
2016-09-23 20:35 ` Peter Zijlstra
2016-09-23 22:34 ` Andi Kleen
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