From: Hannes Reinecke <hare@suse.de>
To: John Garry <john.garry@huawei.com>,
bart.vanassche@sandisk.com, hch@infradead.org,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
Subject: Re: scsi-mq performance check
Date: Fri, 18 Dec 2015 16:08:24 +0100 [thread overview]
Message-ID: <56742168.6030200@suse.de> (raw)
In-Reply-To: <56741F04.3070506@huawei.com>
On 12/18/2015 03:58 PM, John Garry wrote:
> Hi,
>
> I have started to enable scsi-mq on the HiSilicon SAS driver.
>
> Are there hints/checks I should use to make sure it is configured
> correctly/optimally? In my initial testing I have seen some
> performance improvements, but none like what I have seen in
> presentations.
>
The whole thing is build around having symmetric submit and receive
queues, so that we can tack a send/receive queue pair to the same
CPU. With that we can ensure that we don't have any cache
invalidation, as the request is already in the cache for that CPU
when the completion is recieved. _And_ we can get rid of most
spinlocks as other CPUs cannot access our request.
So make sure to have the submit and receive queues properly done,
and ensure you don't have any global resources within your driver
which needs to be locked. Or move access to those resources out of
the fast path.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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next prev parent reply other threads:[~2015-12-18 15:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-18 14:58 scsi-mq performance check John Garry
2015-12-18 15:08 ` Hannes Reinecke [this message]
2015-12-18 15:19 ` Bart Van Assche
2015-12-18 15:36 ` John Garry
2015-12-18 16:05 ` Hannes Reinecke
2015-12-18 16:50 ` John Garry
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