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From:   SeongJae Park <sj@kernel.org>
To:     SeongJae Park <sj@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>, damon@lists.linux.dev,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Subject: Re: [PATCH 1/2] mm/damon/sysfs: remove requested targets when online-commit inputs
Date:   Sat, 28 Oct 2023 21:09:30 +0000
Message-Id: <20231028210930.62947-1-sj@kernel.org>
In-Reply-To: <20231022210735.46409-2-sj@kernel.org>
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On Sun, 22 Oct 2023 21:07:33 +0000 SeongJae Park <sj@kernel.org> wrote:

> damon_sysfs_set_targets(), which updates the targets of the context for
> online commitment, do not remove targets that removed from the
> corresponding sysfs files.  As a result, more than intended targets of
> the context can exist and hence consume memory and monitoring CPU
> resource more than expected.
> 
> Fix it by removing all targets of the context and fill up again using
> the user input.  This could cause unnecessary memory dealloc and realloc
> operations, but this is not a hot code path.  Also, note that
> damon_target is stateless, and hence no data is lost.

This is not true.  'struct damon_target' contains monitoring results
(regions_list).  Hence, this patch makes all monitoring results to be removed
whenever doing online-commit.  I was confused with init_regions at the time of
this writing, sorry.

I will send a fix for this soon.


Thanks,
SJ