From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "ming.lei@redhat.com" <ming.lei@redhat.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"tom81094@gmail.com" <tom81094@gmail.com>,
"himanshu.madhani@cavium.com" <himanshu.madhani@cavium.com>,
"paolo.valente@linaro.org" <paolo.valente@linaro.org>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"oleksandr@natalenko.name" <oleksandr@natalenko.name>,
"john.garry@huawei.com" <john.garry@huawei.com>,
"osandov@fb.com" <osandov@fb.com>,
"loberman@redhat.com" <loberman@redhat.com>,
"james.smart@broadcom.com" <james.smart@broadcom.com>
Subject: Re: [PATCH V7 4/6] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops
Date: Fri, 13 Oct 2017 17:08:52 +0000 [thread overview]
Message-ID: <1507914527.13345.17.camel@wdc.com> (raw)
In-Reply-To: <20171013164519.GF30899@ming.t460p>
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WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "ming.lei@redhat.com" <ming.lei@redhat.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"tom81094@gmail.com" <tom81094@gmail.com>,
"himanshu.madhani@cavium.com" <himanshu.madhani@cavium.com>,
"paolo.valente@linaro.org" <paolo.valente@linaro.org>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"oleksandr@natalenko.name" <oleksandr@natalenko.name>,
"john.garry@huawei.com" <john.garry@huawei.com>,
"osandov@fb.com" <osandov@fb.com>,
"loberman@redhat.com" <loberman@redhat.com>,
"james.smart@broadcom.com" <james.smart@broadcom.com>
Subject: Re: [PATCH V7 4/6] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops
Date: Fri, 13 Oct 2017 17:08:52 +0000 [thread overview]
Message-ID: <1507914527.13345.17.camel@wdc.com> (raw)
In-Reply-To: <20171013164519.GF30899@ming.t460p>
On Sat, 2017-10-14 at 00:45 +0800, Ming Lei wrote:
> On Fri, Oct 13, 2017 at 04:31:04PM +0000, Bart Van Assche wrote:
> > On Sat, 2017-10-14 at 00:07 +0800, Ming Lei wrote:
> > > Actually it is in hot path, for example, lpfc and qla2xx's queue depth is 3,
> >
> > Sorry but I doubt whether that is correct. More in general, I don't know any modern
> > storage HBA for which the default queue depth is so low.
>
> You can grep:
>
> [ming@ming linux]$ git grep -n cmd_per_lun ./drivers/scsi/ | grep -E "qla2xxx|lpfc"
Such a low queue depth will result in suboptimal performance for adapters
that communicate over a storage network. I think that's a bug and that both
adapters support much higher cmd_per_lun values.
(+James Smart)
James, can you explain us why commit 445cf4f4d2aa decreased LPFC_CMD_PER_LUN
from 30 to 3? Was that perhaps a workaround for a bug in a specific target
implementation?
(+Himanshu Madhani)
Himanshu, do you perhaps know whether it is safe to increase cmd_per_lun for
the qla2xxx initiator driver to the scsi_host->can_queue value?
> Even SRP/IB isn't big too, just 32.
The default value for ib_srp for cmd_per_lun is 62 but that value can be
overridden by selecting another value in /etc/default/srp_daemon.conf. Note:
a lower value is selected if after SRP login it becomes clear that the target
queue depth is lower than the cmd_per_lun value requested by the user. This
is a performance optimization and avoids that the SRP target system has to
send back BUSY responses to the initiator.
Bart.
next prev parent reply other threads:[~2017-10-13 17:08 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-12 18:36 [PATCH V7 0/6] blk-mq-sched: improve sequential I/O performance Ming Lei
2017-10-12 18:36 ` [PATCH V7 1/6] blk-mq-sched: fix scheduler bad performance Ming Lei
2017-10-12 18:37 ` [PATCH V7 2/6] blk-mq-sched: move actual dispatching into one helper Ming Lei
2017-10-12 18:37 ` [PATCH V7 3/6] sbitmap: introduce __sbitmap_for_each_set() Ming Lei
2017-10-12 18:37 ` [PATCH V7 4/6] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops Ming Lei
2017-10-12 18:46 ` Jens Axboe
2017-10-13 0:19 ` Ming Lei
2017-10-13 14:44 ` Jens Axboe
2017-10-13 16:07 ` Ming Lei
2017-10-13 16:19 ` Jens Axboe
2017-10-13 16:21 ` Ming Lei
2017-10-13 16:28 ` Jens Axboe
2017-10-13 16:31 ` Bart Van Assche
2017-10-13 16:31 ` Bart Van Assche
2017-10-13 16:33 ` Jens Axboe
2017-10-13 16:45 ` Ming Lei
2017-10-13 17:08 ` Bart Van Assche [this message]
2017-10-13 17:08 ` Bart Van Assche
2017-10-13 17:29 ` Ming Lei
2017-10-13 17:47 ` Bart Van Assche
2017-10-13 17:47 ` Bart Van Assche
2017-10-16 11:30 ` Hannes Reinecke
2017-10-16 16:06 ` Bart Van Assche
2017-10-16 16:06 ` Bart Van Assche
2017-10-17 1:29 ` Ming Lei
2017-10-17 6:38 ` Hannes Reinecke
2017-10-17 9:36 ` Ming Lei
2017-10-17 18:09 ` Bart Van Assche
2017-10-13 16:17 ` Ming Lei
2017-10-13 16:20 ` Jens Axboe
2017-10-13 16:22 ` Ming Lei
2017-10-13 16:28 ` Jens Axboe
2017-10-12 18:37 ` [PATCH V7 5/6] blk-mq-sched: improve dispatching from sw queue Ming Lei
2017-10-12 18:48 ` Bart Van Assche
2017-10-13 0:20 ` Ming Lei
2017-10-12 18:37 ` [PATCH V7 6/6] SCSI: implement .get_budget and .put_budget for blk-mq Ming Lei
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