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From:   SeongJae Park <sj@kernel.org>
To:     Xin Hao <xhao@linux.alibaba.com>
Cc:     sj@kernel.org, akpm@linux-foundation.org, damon@lists.linux.dev,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 1/2] mm/damon/lru_sort: Move target memory region check to head of func
Date:   Thu, 18 Aug 2022 17:11:45 +0000
Message-Id: <20220818171145.51607-1-sj@kernel.org>
In-Reply-To: <20220818105732.34492-2-xhao@linux.alibaba.com>
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Hi Xin,


On Thu, 18 Aug 2022 18:57:31 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:

> In damon_lru_sort_apply_parameters(), if "monitor_region_start"
> and "monitor_region_end" is not a valid physical address range,
> There no need to run the remainder codes in it.

The function, 'damon_lru_sort_apply_parameters()', checks validity of
parameters and construct the DAMON context one by one.  For example,
'damon_set_attrs()' returns an error if the parameters are invalid.  So the
intended flow is,

1. check DAMON attributes parameters,
2. apply DAMON attributes parameters,
3. check scheme parameters,
4. apply scheme parameters,
5. check target region parameters, and
6. apply target region parameters.

Therefore what this patch does is making the target regions validity check to
be done earlier than validity checks of other parameters.  There is no special
reason to check the region earlier than others.  Also, this change makes the
flow of the function a little bit weird in my humble opinion, as the flow will
be

1. check target region parameters,
2. check DAMON attributes parameters,
3. apply DAMON attributes parameters,
4. check scheme parameters,
5. apply scheme parameters, and
6. apply target region parameters.

So I'd argue this patch seems not really needed, sorry.


Thanks,
SJ

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