From: Damien Le Moal <damien.lemoal@opensource.wdc.com>
To: Bart Van Assche <bvanassche@acm.org>, Jens Axboe <axboe@kernel.dk>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Jaegeuk Kim <jaegeuk@kernel.org>,
Niklas Cassel <Niklas.Cassel@wdc.com>,
Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 3/4] block/mq-deadline: Stop using per-CPU counters
Date: Mon, 27 Sep 2021 12:41:31 +0900 [thread overview]
Message-ID: <2be46ef0-8848-a097-4099-31f8103b53ad@opensource.wdc.com> (raw)
In-Reply-To: <9997e3dc-44f8-1884-04f9-fc43dc655d5d@acm.org>
On 2021/09/27 11:38, Bart Van Assche wrote:
> On 9/26/21 17:19, Damien Le Moal wrote:
>> Another thing: in patch 3, you are actually not handling the overflows. So
>> dd_queued() may return some very weird number (temporarily) when the inserted
>> count overflows before the completed count does. Since
>> dd_dispatch_aged_requests() does not care about the actual value of dd_queued(),
>> only if it is 0 or not, I am not 100% sure if it is useful to fix. Except maybe
>> for sysfs attributes ?
>
> Hmm ... I'm not following. I think it can be proven mathematically that
> dd_queued() returns a number in the range [0, max_queued_requests). Here is
> an example:
> * inserted = 1 (wrapped around).
> * completed = UINT32_MAX - 1 (about to wrap but has not yet wrapped around).
> * dd_queued() returns 2.
You mean 3, right ?
But yes... Slow Monday, I need more coffee :)
Cheers.
--
Damien Le Moal
Western Digital Research
next prev parent reply other threads:[~2021-09-27 3:41 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-23 23:23 [PATCH 0/4] Restore I/O priority support in the mq-deadline scheduler Bart Van Assche
2021-09-23 23:26 ` [PATCH 1/4] block/mq-deadline: Improve request accounting further Bart Van Assche
2021-09-23 23:26 ` [PATCH 2/4] block/mq-deadline: Add an invariant check Bart Van Assche
2021-09-24 10:54 ` Damien Le Moal
2021-09-27 15:53 ` Niklas Cassel
2021-09-23 23:26 ` [PATCH 3/4] block/mq-deadline: Stop using per-CPU counters Bart Van Assche
2021-09-24 10:58 ` Damien Le Moal
2021-09-25 2:59 ` Bart Van Assche
2021-09-27 0:19 ` Damien Le Moal
2021-09-27 2:38 ` Bart Van Assche
2021-09-27 3:41 ` Damien Le Moal [this message]
2021-09-27 15:53 ` Niklas Cassel
2021-09-23 23:26 ` [PATCH 4/4] block/mq-deadline: Prioritize high-priority requests Bart Van Assche
2021-09-24 11:08 ` Damien Le Moal
2021-09-27 20:03 ` Bart Van Assche
2021-09-24 10:54 ` [PATCH 1/4] block/mq-deadline: Improve request accounting further Damien Le Moal
2021-09-27 15:53 ` Niklas Cassel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2be46ef0-8848-a097-4099-31f8103b53ad@opensource.wdc.com \
--to=damien.lemoal@opensource.wdc.com \
--cc=Niklas.Cassel@wdc.com \
--cc=axboe@kernel.dk \
--cc=bvanassche@acm.org \
--cc=hare@suse.de \
--cc=hch@lst.de \
--cc=jaegeuk@kernel.org \
--cc=linux-block@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).