From: Bart Van Assche <bvanassche@acm.org>
To: Damien Le Moal <dlemoal@kernel.org>,
"Martin K . Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
John Garry <john.g.garry@oracle.com>,
Hannes Reinecke <hare@suse.de>,
Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>, Ming Lei <ming.lei@redhat.com>,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Subject: Re: [PATCH v4 6/6] scsi: core: Improve IOPS in case of host-wide tags
Date: Fri, 19 Dec 2025 09:35:13 -0800 [thread overview]
Message-ID: <dba8da69-1f14-48a5-a540-01e8659b7d3a@acm.org> (raw)
In-Reply-To: <ac537693-ec0c-4c50-8ee9-a02975f0e18c@kernel.org>
On 12/16/25 7:24 PM, Damien Le Moal wrote:
> On 12/17/25 07:30, Bart Van Assche wrote:
>> The SCSI core uses the budget map to restrict the number of commands
>> that are in flight per logical unit. That limit check can be left out if
>> host->cmd_per_lun >= host->can_queue and if the host tag set is shared
>> across all hardware queues or if there is only one hardware queue Since
>
> Missing a period at the end of the sentence (before Since). But more
> importantly, this does not explain why the above is true, and frankly, I do not
> see it...
Hi Damien,
The purpose of the SCSI device budget map is to prevent that the queue
depth limit for that SCSI device is exceeded. If there is only a single
hardware queue or there is a host-wide tag set and host->cmd_per_lun is
identical to host->can_queue, it is not possible that the queue depth
for a single SCSI device is exceeded and hence the SCSI device budget
map is not needed.
Please help with reviewing the ATA patch in this series.
Thanks,
Bart.
next prev parent reply other threads:[~2025-12-19 17:35 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-16 22:30 [PATCH v4 0/6] Increase SCSI IOPS Bart Van Assche
2025-12-16 22:30 ` [PATCH v4 1/6] block: Rename busy_tag_iter_fn into blk_mq_rq_iter_fn Bart Van Assche
2025-12-16 22:30 ` [PATCH v4 2/6] block: Introduce __blk_mq_tagset_iter() Bart Van Assche
2025-12-16 22:30 ` [PATCH v4 3/6] block: Introduce blk_mq_tagset_iter() Bart Van Assche
2025-12-16 22:30 ` [PATCH v4 4/6] ata: libata: Set .needs_budget_token Bart Van Assche
2025-12-16 22:30 ` [PATCH v4 5/6] scsi: core: Generalize scsi_device_busy() Bart Van Assche
2025-12-16 22:30 ` [PATCH v4 6/6] scsi: core: Improve IOPS in case of host-wide tags Bart Van Assche
2025-12-17 3:24 ` Damien Le Moal
2025-12-19 17:35 ` Bart Van Assche [this message]
2025-12-19 23:06 ` Damien Le Moal
2025-12-20 0:05 ` Bart Van Assche
2025-12-20 0:13 ` Damien Le Moal
2025-12-20 0:28 ` Bart Van Assche
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=dba8da69-1f14-48a5-a540-01e8659b7d3a@acm.org \
--to=bvanassche@acm.org \
--cc=James.Bottomley@HansenPartnership.com \
--cc=axboe@kernel.dk \
--cc=dlemoal@kernel.org \
--cc=hare@suse.de \
--cc=hch@infradead.org \
--cc=john.g.garry@oracle.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=ming.lei@redhat.com \
/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