From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: "Ewan D. Milne" <emilne@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>,
Hannes Reinecke <hare@suse.de>, Ming Lei <ming.lei@redhat.com>,
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>,
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: Thu, 21 Nov 2019 21:25:25 -0500 [thread overview]
Message-ID: <yq1tv6wbqay.fsf@oracle.com> (raw)
In-Reply-To: <f5b78ec7c0e6fec69950cace8531eb342987c0b9.camel@redhat.com> (Ewan D. Milne's message of "Wed, 20 Nov 2019 16:36:41 -0500")
Ewan,
> Delaying the queue re-run vs. a ramp down might negatively affect
> performance. I'm not sure how accurate the ramp is at discovering the
> optimum though.
The optimum - as well as the actual limit - might change over time in a
multi-initiator setup as other hosts grab resources on the device.
I do think that the only way forward here, if we want to avoid counting
outstanding commands for performance reasons, is to ensure that the
BUSY/QUEUE_FULL/TASK_SET_FULL handling is relatively fast path and not
something deep in the bowels of error handling. Which it actually
isn't. But I do think we'll need to take a closer look.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2019-11-22 2:25 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 [this message]
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
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
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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