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From: Peter Zijlstra <peterz@infradead.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, acme@redhat.com,
	kirill.shutemov@linux.intel.com, Borislav Petkov <bp@alien8.de>,
	rric@kernel.org
Subject: Re: [RFC PATCH 09/17] perf: Use shmemfs pages for userspace-only per-thread detached events
Date: Tue, 3 Oct 2017 16:43:35 +0200	[thread overview]
Message-ID: <20171003144335.jqsraoqn2zskv2xd@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170905133026.13689-10-alexander.shishkin@linux.intel.com>

On Tue, Sep 05, 2017 at 04:30:18PM +0300, Alexander Shishkin wrote:
> In order to work around the problem of using up mlocked memory for the
> detached events, we can pin the ring buffer pages only while they are
> in use (that is, the event is ACTIVE), and unpin them for the rest of
> the time. When not pinned in, these pages can be swapped out. This way,
> one user can have at most mlock_limit*nr_cpus kB of memory pinned at
> any given moment, however many events they actually have.
> 
> This enforces a constraint: pinning and unpinning may sleep and thus
> can't be done in the event scheduling path. Instead, we use a task
> work to do this, which this pattern us to userspace-only events.
> Also, since one userspace thread only needs one buffer (for whatever
> CPU it's running on at any given moment), we only do this for per-thread
> events.
> 
> The source for such swappable pages is shmemfs. This patch allows
> allocating perf ring buffer pages from an shmemfs file if the above
> constraints are met.

Right, so why still allow that previous icky thing? What cases do we
need that for?

  reply	other threads:[~2017-10-03 14:43 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-05 13:30 [RFC PATCH 00/17] perf: Detached events Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 01/17] perf: Allow mmapping only user page Alexander Shishkin
2017-09-06 16:28   ` Borislav Petkov
2017-09-13 11:35     ` Alexander Shishkin
2017-09-13 12:58       ` Borislav Petkov
2017-09-05 13:30 ` [RFC PATCH 02/17] perf: Factor out mlock accounting Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 03/17] tracefs: De-globalize instances' callbacks Alexander Shishkin
2018-01-24 18:54   ` Steven Rostedt
2017-09-05 13:30 ` [RFC PATCH 04/17] tracefs: Add ->unlink callback to tracefs_dir_ops Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 05/17] perf: Introduce detached events Alexander Shishkin
2017-10-03 14:34   ` Peter Zijlstra
2017-10-06 11:23     ` Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 06/17] perf: Add buffers to the " Alexander Shishkin
2017-10-03 14:36   ` Peter Zijlstra
2017-09-05 13:30 ` [RFC PATCH 07/17] perf: Add pmu_info to user page Alexander Shishkin
2017-10-03 14:40   ` Peter Zijlstra
2017-09-05 13:30 ` [RFC PATCH 08/17] perf: Allow inheritance for detached events Alexander Shishkin
2017-10-03 14:42   ` Peter Zijlstra
2017-10-06 11:40     ` Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 09/17] perf: Use shmemfs pages for userspace-only per-thread " Alexander Shishkin
2017-10-03 14:43   ` Peter Zijlstra [this message]
2017-10-06 11:52     ` Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 10/17] perf: Implement pinning and scheduling for SHMEM events Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 11/17] perf: Implement mlock accounting for shmem ring buffers Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 12/17] perf: Track pinned events per user Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 13/17] perf: Re-inject shmem buffers after exec Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 14/17] perf: Add ioctl(REATTACH) for detached events Alexander Shishkin
2017-10-03 14:50   ` Peter Zijlstra
2017-09-05 13:30 ` [RFC PATCH 15/17] perf: Allow controlled non-root access to " Alexander Shishkin
2017-10-03 14:53   ` Peter Zijlstra
2017-09-05 13:30 ` [RFC PATCH 16/17] perf/x86/intel/pt: Add PMU info Alexander Shishkin
2017-09-05 13:30 ` [RFC PATCH 17/17] perf/x86/intel/bts: " Alexander Shishkin
2017-09-06 16:24 ` [RFC PATCH 00/17] perf: Detached events Borislav Petkov
2017-09-13 11:54   ` Alexander Shishkin

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