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 <20240509023937.1090421-3-zhaoyang.huang@unisoc.com> <ZjzEH5fFGHgnqbLj@infradead.org>
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From: Zhaoyang Huang <huangzhaoyang@gmail.com>
Date: Fri, 10 May 2024 11:06:14 +0800
Message-ID: <CAGWkznG4xodugVdbKZCn99UiQT5Z3oHYLhTsvOCoe_VNxUVvnw@mail.gmail.com>
Subject: Re: [RFC PATCH 2/2] mm: introduce budgt control in readahead
To: Christoph Hellwig <hch@infradead.org>
Cc: "zhaoyang.huang" <zhaoyang.huang@unisoc.com>, Andrew Morton <akpm@linux-foundation.org>, 
	Matthew Wilcox <willy@infradead.org>, Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>, 
	Josef Bacik <josef@toxicpanda.com>, Baolin Wang <baolin.wang@linux.alibaba.com>, linux-mm@kvack.org, 
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, 
	cgroups@vger.kernel.org, steve.kang@unisoc.com
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On Thu, May 9, 2024 at 8:40=E2=80=AFPM Christoph Hellwig <hch@infradead.org=
> wrote:
>
> > +     unsigned long budgt =3D inode->i_sb->s_bdev ?
> > +                     blk_throttle_budgt(inode->i_sb->s_bdev) : 0;
>
> The readahead code is used for all file systems, you can't just call
> into block layer code here.
>
ok. I would like to know any suggestions on introducing throttle
budget control into readahead which actually works as a negative
feedback path. IMO, negative feedback is a good methodology which has
been used in scheduler(EAS) and thermal control(IPA) and
memory(MGLRU). I would like to suggest to have a try on have it work
cross the boundary of memory and block layer.

vfs_read / page fault
|
readahead  <---------|
|                               |
aops->readpages    |
|                               |
block_layer------------