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Message-ID: <20231003205022.58ffcb2a@gandalf.local.home>
Date: Tue, 3 Oct 2023 20:50:22 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: SeongJae Park <sj@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, damon@...ts.linux.dev,
linux-mm@...ck.org, linux-trace-kernel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v2 1/2] mm/damon/core: add a tracepoint for damos
apply target regions
On Wed, 13 Sep 2023 02:20:49 +0000
SeongJae Park <sj@...nel.org> wrote:
> DAMON provides damon_aggregated tracepoint, which exposes details of
> each region and its access monitoring results. It is useful for
> getting whole monitoring results, e.g., for recording purposes.
>
> For investigations of DAMOS, DAMON Sysfs interface provides DAMOS
> statistics and tried_regions directory. But, those provides only
> statistics and snapshots. If the scheme is frequently applied and if
> the user needs to know every detail of DAMOS behavior, the
> snapshot-based interface could be insufficient and expensive.
>
> As a last resort, userspace users need to record the all monitoring
> results via damon_aggregated tracepoint and simulate how DAMOS would
> worked. It is unnecessarily complicated. DAMON kernel API users,
> meanwhile, can do that easily via before_damos_apply() callback field of
> 'struct damon_callback', though.
>
> Add a tracepoint that will be called just after before_damos_apply()
> callback for more convenient investigations of DAMOS. The tracepoint
> exposes all details about each regions, similar to damon_aggregated
> tracepoint.
>
> Please note that DAMOS is currently not only for memory management but
> also for query-like efficient monitoring results retrievals (when 'stat'
> action is used). Until now, only statistics or snapshots were
> supported. Addition of this tracepoint allows efficient full recording
> of DAMOS-based filtered monitoring results.
>
>From a tracing point of view.
Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
-- Steve
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