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Date:   Tue, 19 Jul 2022 23:04:36 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     CGEL <cgel.zte@gmail.com>
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Subject: Re: [PATCH] fs: drop_caches: skip dropping pagecache which is always
 dirty
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On Wed, Jul 20, 2022 at 06:02:32AM +0000, CGEL wrote:
> For example, some systems will create a lot of pagecache when boot up
> while reading bzImage, ramdisk, docker images etc. Most of this pagecache
> is useless after boot up. It may has a longterm negative effects for the
> workload when trigger page reclaim. It is especially harmful when trigger
> direct_reclaim or we need allocate pages in atomic context. So users may
> chose to drop_caches after boot up.

It is purely a debug interface.  If you want to drop specific page cache
that needs to be done through madvise.