linux-kernel - Re: [RFC PATCH 0/2] mm/damon/stat: expose auto-tuned intervals and non-idle ages

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Message-Id: <20250912020619.59642-1-sj@kernel.org>
Date: Thu, 11 Sep 2025 19:06:19 -0700
From: SeongJae Park <sj@...nel.org>
To: SeongJae Park <sj@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	damon@...ts.linux.dev,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC PATCH 0/2] mm/damon/stat: expose auto-tuned intervals and non-idle ages

On Tue,  9 Sep 2025 21:00:20 -0700 SeongJae Park <sj@...nel.org> wrote:

> DAMON_STAT is intentionally providing limited information for easy
> consumption.  From production fleet level usages, below limitations are
> found, though.
> 
> The aggregation interval of DAMON_STAT represents the granularity of the
> memory_idle_ms_percentiles.  But it is auto-tuned and not exposed to
> users, so users cannot know the granularity.
> 
> All memory regions of non-zero (positive) nr_accesses are treated as
> having zero idle time.  A significant portion of production systems have
> such zero idle time.  Hence breakdown of warm and hot data is
> impossible.
> 
> To overcome the limitations, expose the auto-tuned aggregation interval
> with a new parameter named xxx and the age of non-zero nr_accesses

s/xx/aggr_interval_us/

Forgot updating that before posting, sorry.  The next version should fix it.


Thanks,
SJ

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