Re: [PATCH] fs: drop_caches: skip dropping pagecache which is always dirty

[CGEL]

On Tue, Jul 19, 2022 at 11:04:36PM -0700, Christoph Hellwig wrote:
> 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.

It's not easy for users to use madvise in complex system, it takes cost.
Since drop_caches is not forbidden, and users may want simply use it in
the scene above mail described.