From: James Smart <james.smart@broadcom.com>
To: Bart Van Assche <bvanassche@acm.org>,
Ming Lei <ming.lei@redhat.com>, Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
"James E . J . Bottomley" <jejb@linux.ibm.com>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
linux-scsi@vger.kernel.org,
Sathya Prakash <sathya.prakash@broadcom.com>,
Chaitra P B <chaitra.basappa@broadcom.com>,
Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>,
Kashyap Desai <kashyap.desai@broadcom.com>,
Sumit Saxena <sumit.saxena@broadcom.com>,
Shivasharan S <shivasharan.srikanteshwara@broadcom.com>,
"Ewan D . Milne" <emilne@redhat.com>,
Christoph Hellwig <hch@lst.de>,
Bart Van Assche <bart.vanassche@wdc.com>
Subject: Re: [PATCH 4/4] scsi: core: don't limit per-LUN queue depth for SSD
Date: Fri, 22 Nov 2019 10:26:11 -0800 [thread overview]
Message-ID: <7e44d961-a089-e073-1e35-5890e75b0ba7@broadcom.com> (raw)
In-Reply-To: <5f84476f-95b4-79b6-f72d-4e2de447065c@acm.org>
On 11/22/2019 10:14 AM, Bart Van Assche wrote:
> Thanks for having shared these numbers. I think this is very useful
> information. Do these results show the performance drop that happens
> if /sys/block/.../device/queue_depth exceeds .can_queue? What I am
> wondering about is how important these results are in the context of
> this discussion. Are there any modern SCSI devices for which a SCSI
> LLD sets scsi_host->can_queue and scsi_host->cmd_per_lun such that the
> device responds with BUSY? What surprised me is that only three SCSI
> LLDs call scsi_track_queue_full() (mptsas, bfa, esp_scsi). Does that
> mean that BUSY responses from a SCSI device or HBA are rare?
That's because most of the drivers, which had queue full ramp up/ramp
down in them and would have called scsi_track_queue_full() converted
over to the moved-queue-full-handling-in-the-mid-layer, indicated by
sht->track_queue_depth = 1.
Yes - it is still hit a lot!
-- james
next prev parent reply other threads:[~2019-11-22 18:26 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-18 10:31 [PATCH 0/4] scis: don't apply per-LUN queue depth for SSD Ming Lei
2019-11-18 10:31 ` [PATCH 1/4] scsi: megaraid_sas: use private counter for tracking inflight per-LUN commands Ming Lei
2019-11-20 9:54 ` Hannes Reinecke
2019-11-26 3:12 ` Kashyap Desai
2019-11-26 3:37 ` Ming Lei
2019-12-05 10:32 ` Kashyap Desai
2019-11-18 10:31 ` [PATCH 2/4] scsi: mpt3sas: " Ming Lei
2019-11-20 9:55 ` Hannes Reinecke
2019-11-18 10:31 ` [PATCH 3/4] scsi: sd: register request queue after sd_revalidate_disk is done Ming Lei
2019-11-20 9:59 ` Hannes Reinecke
2019-11-18 10:31 ` [PATCH 4/4] scsi: core: don't limit per-LUN queue depth for SSD Ming Lei
2019-11-20 10:05 ` Hannes Reinecke
2019-11-20 17:00 ` Ewan D. Milne
2019-11-20 20:56 ` Bart Van Assche
2019-11-20 21:36 ` Ewan D. Milne
2019-11-22 2:25 ` Martin K. Petersen
2019-11-21 1:07 ` Ming Lei
2019-11-22 2:59 ` Martin K. Petersen
2019-11-22 3:24 ` Ming Lei
2019-11-22 16:38 ` Sumanesh Samanta
2019-11-21 0:08 ` Sumanesh Samanta
2019-11-21 0:54 ` Ming Lei
2019-11-21 19:19 ` Ewan D. Milne
2019-11-21 0:53 ` Ming Lei
2019-11-21 15:45 ` Hannes Reinecke
2019-11-22 8:09 ` Ming Lei
2019-11-22 18:14 ` Bart Van Assche
2019-11-22 18:26 ` James Smart [this message]
2019-11-22 20:46 ` Bart Van Assche
2019-11-22 22:04 ` Ming Lei
2019-11-22 22:00 ` Ming Lei
2019-11-25 18:28 ` Ewan D. Milne
2019-11-25 22:14 ` James Smart
2019-11-22 2:18 ` Martin K. Petersen
-- strict thread matches above, loose matches on Subject: below --
2019-11-20 21:58 Sumanesh Samanta
2019-11-21 1:21 ` Ming Lei
2019-11-21 1:50 ` Sumanesh Samanta
2019-11-21 2:23 ` Ming Lei
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