From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
Jaegeuk Kim <jaegeuk@kernel.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Martijn Coenen <maco@android.com>
Subject: Re: [PATCH v2 2/3] loop: Select I/O scheduler 'none' from inside add_disk()
Date: Thu, 5 Aug 2021 09:49:00 -0700 [thread overview]
Message-ID: <ed738693-0a08-8047-7300-e84b4e3b6cd5@acm.org> (raw)
In-Reply-To: <YQtaWz7EtkNAtIkY@T590>
On 8/4/21 8:26 PM, Ming Lei wrote:
> On Wed, Aug 04, 2021 at 10:43:05AM -0700, Bart Van Assche wrote:
>> Thanks for having suggested an alternative. However, isn't the above a
>> policy? Shouldn't a kernel provide mechanisms instead of policies?
>
> REQ_SWAP means it is one IO written to swap device/file, so the system
> is suffering memory pressure, then isn't it reasonable to bypass io
> scheduler for all SWAP IOs?
Hmm ... I'm not sure that approach is ideal when swapping to a hard disk.
>> Additionally, the above patch does not address all Android loop driver use
>> cases. Reading APEX files is regular I/O and hence REQ_SWAP is not set while
>> reading from APEX files.
>
> Is APEX file one swap file? If not, can you explain it a bit why you want to
> switch to none when reading APEX file?
As far as I know Android uses the loop driver for two purposes:
- A zram instance is used as swap device and the zram instance is
configured to use a loop device.
- apexd mounts APEX files read-only and uses the loop driver to access
these files as a block device.
Bart.
next prev parent reply other threads:[~2021-08-05 16:49 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-03 18:23 [PATCH v2 0/3] Improve loop driver I/O scheduler and QD selection Bart Van Assche
2021-08-03 18:23 ` [PATCH v2 1/3] blk-mq: Introduce the BLK_MQ_F_NO_SCHED_BY_DEFAULT flag Bart Van Assche
2021-08-03 18:23 ` [PATCH v2 2/3] loop: Select I/O scheduler 'none' from inside add_disk() Bart Van Assche
2021-08-04 2:39 ` Ming Lei
2021-08-04 17:43 ` Bart Van Assche
2021-08-05 3:26 ` Ming Lei
2021-08-05 16:49 ` Bart Van Assche [this message]
2021-08-04 17:58 ` Jens Axboe
2021-08-04 5:35 ` Christoph Hellwig
2021-08-04 17:58 ` Bart Van Assche
2021-08-04 18:04 ` Jens Axboe
2021-08-05 6:39 ` Christoph Hellwig
2021-08-03 18:23 ` [PATCH v2 3/3] loop: Add the default_queue_depth kernel module parameter Bart Van Assche
2021-08-04 6:07 ` Greg KH
2021-08-04 17:38 ` Bart Van Assche
2021-08-04 19:33 ` Greg KH
2021-08-05 6:14 ` Chaitanya Kulkarni
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