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From: Zhaoyang Huang <huangzhaoyang@gmail.com>
Date: Thu, 25 Jan 2024 15:52:16 +0800
Message-ID: <CAGWkznHK5UPajY2PG24Jm7+A0c9q+tyQzrPdd=n3tp0dgX+T0w@mail.gmail.com>
Subject: Re: [PATCHv3 1/1] block: introduce content activity based ioprio
To: Damien Le Moal <dlemoal@kernel.org>
Cc: "zhaoyang.huang" <zhaoyang.huang@unisoc.com>, Andrew Morton <akpm@linux-foundation.org>, 
	Jens Axboe <axboe@kernel.dk>, Yu Zhao <yuzhao@google.com>, 
	Niklas Cassel <niklas.cassel@wdc.com>, "Martin K . Petersen" <martin.petersen@oracle.com>, 
	Hannes Reinecke <hare@suse.de>, Linus Walleij <linus.walleij@linaro.org>, linux-mm@kvack.org, 
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, 
	steve.kang@unisoc.com
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On Thu, Jan 25, 2024 at 3:40=E2=80=AFPM Damien Le Moal <dlemoal@kernel.org>=
 wrote:
>
> On 1/25/24 16:19, zhaoyang.huang wrote:
> > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> >
> > Currently, request's ioprio are set via task's schedule priority(when n=
o
> > blkcg configured), which has high priority tasks possess the privilege =
on
> > both of CPU and IO scheduling.
> > This commit works as a hint of original policy by promoting the request=
 ioprio
> > based on the page/folio's activity. The original idea comes from LRU_GE=
N
> > which provides more precised folio activity than before. This commit tr=
y
> > to adjust the request's ioprio when certain part of its folios are hot,
> > which indicate that this request carry important contents and need be
> > scheduled ealier.
> >
> > This commit is verified on a v6.6 6GB RAM android14 system via 4 test c=
ases
> > by changing the bio_add_page/folio API in ext4 and f2fs.
>
> And as mentioned already by Chrisoph and Jens, why don't you just simply =
set
> bio->bi_ioprio to the value you want before calling submit_bio() in these=
 file
> systems ? Why all the hacking of the priority code for that ? That is not
> justified at all.
>
> Furthermore, the activity things reduces the ioprio hint bits to the bare
> minimum 3 bits necessary for command duration limits. Not great. But if y=
ou
> simply set the prio class based on your activity algorithm, you do not ne=
ed to
> change all that.
That is because bio->io_prio changes during bio grows with adding
different activity pages in. I have to wrap these into an API which
has both of fs and block be transparent to the process.
>
> Note: Your patch is full of whitespace changes.
Sorry, I double checked the source code and the patch with
checkpatch.pl again, no whitespace found, don't know why
>
> --
> Damien Le Moal
> Western Digital Research
>