linux-kernel - Re: [PATCH] mm : sync ra->ra_pages with bdi->ra

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Message-ID: <CAGWkznFYaMLUf3cazP9x9eA-SYTu6GkXR=m3q20WowGsCZLWHw@mail.gmail.com>
Date:   Mon, 17 Aug 2020 18:59:27 +0800
From:   Zhaoyang Huang <huangzhaoyang@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Roman Gushchin <klamm@...dex-team.ru>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm : sync ra->ra_pages with bdi->ra_pages

On Sat, Aug 15, 2020 at 12:15 PM Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> On Fri, 14 Aug 2020 13:10:34 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> > On Fri, 14 Aug 2020 17:03:44 +0800 Zhaoyang Huang <huangzhaoyang@...il.com> wrote:
> >
> > > Some system(like android) will turbo read during startup via expanding the
> > > readahead window and then set it back to normal(128kb as usual). However, some
> > > files in the system process context will keep to be opened since it is opened
> > > up and has no chance to sync with the updated value as it is almost impossible
> > > to change the files attached to the inode(processes are unaware of these things)
> >
> > How about making VM_READAHEAD_PAGES a variable?
>
> Or make it settable in Kconfig?
I don't think so. The scenario I gave before is a dynamic process,
can't be solved via menuconfig thing.