linux-kernel - Re: [PATCH 2/2] mm/damon/vaddr: remove comparison between mm and last

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Date:   Fri, 26 Aug 2022 17:16:29 +0000
From:   SeongJae Park <sj@...nel.org>
To:     xiakaixu1987@...il.com
Cc:     sj@...nel.org, akpm@...ux-foundation.org, damon@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Kaixu Xia <kaixuxia@...cent.com>
Subject: Re: [PATCH 2/2] mm/damon/vaddr: remove comparison between mm and last_mm when checking region accesses

Hi Kaixu,

On Fri, 26 Aug 2022 16:31:18 +0800 xiakaixu1987@...il.com wrote:

> From: Kaixu Xia <kaixuxia@...cent.com>
> 
> The damon regions that belong to the same damon target have the same
> 'struct mm_struct *mm', so it's unnecessary to compare the mm and last_mm
> objects among the damon regions in one damon target when checking accesses.

There could be multiple targets, and 'damon_va_check_accesses()' calls
'__damon_va_check_accesses()' for all the targets.  However,
'damon_va_check_accesses()' doesn't note if '__damon_va_check_accesses()' is
called with a target that same to the target it was called with for the last
time.  Hence the check is necessary.

If I'm missing something, please let me know.

Thanks,
SJ

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