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From: Ming Lei <ming.lei@redhat.com>
To: Mike Christie <michael.christie@oracle.com>
Cc: bvanassche@acm.org, lduncan@suse.com, cleech@redhat.com,
	martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
	james.bottomley@hansenpartnership.com
Subject: Re: [RFC PATCH 1/4] scsi: Allow drivers to set BLK_MQ_F_BLOCKING
Date: Wed, 9 Mar 2022 08:53:34 +0800	[thread overview]
Message-ID: <Yif6jjlpPTEYpcAT@T590> (raw)
In-Reply-To: <20220308003957.123312-2-michael.christie@oracle.com>

On Mon, Mar 07, 2022 at 06:39:54PM -0600, Mike Christie wrote:
> The software iscsi driver's queuecommand can block and taking the extra
> hop from kblockd to its workqueue results in a performance hit. Allowing
> it to set BLK_MQ_F_BLOCKING and transmit from that context directly
> results in a 20-30% improvement in IOPs for workloads like:
> 
> fio --filename=/dev/sdb --direct=1 --rw=randrw --bs=4k --ioengine=libaio
> --iodepth=128  --numjobs=1
> 
> and for all write workloads.

This single patch shouldn't make any difference for iscsi, so please
make it as last one if performance improvement data is provided
in commit log.

Also is there performance effect for other worloads? such as multiple
jobs? iscsi is SQ hardware, so if driver is blocked in ->queuecommand()
via BLK_MQ_F_BLOCKING, other contexts can't submit IO to scsi ML any more.


thanks,
Ming


  parent reply	other threads:[~2022-03-09  1:10 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-08  0:39 [RFC PATCH 0/4] scsi/iscsi: Send iscsi data from kblockd Mike Christie
2022-03-08  0:39 ` [RFC PATCH 1/4] scsi: Allow drivers to set BLK_MQ_F_BLOCKING Mike Christie
2022-03-08  4:57   ` Bart Van Assche
2022-03-09  0:53   ` Ming Lei [this message]
2022-03-09  1:17     ` Mike Christie
2022-03-09  1:43       ` Ming Lei
2022-03-09 19:38         ` Mike Christie
2022-03-08  0:39 ` [RFC PATCH 2/4] scsi: iscsi: Tell drivers when we must not block Mike Christie
2022-03-08  4:59   ` Bart Van Assche
2022-03-08 15:58     ` Mike Christie
2022-03-08  0:39 ` [RFC PATCH 3/4] scsi: iscsi: Support transmit from queuecommand Mike Christie
2022-03-08  0:39 ` [RFC PATCH 4/4] scsi: iscsi_tcp: Allow user to control if " Mike Christie
2022-03-08  5:10   ` Bart Van Assche
2022-03-08 16:51     ` Mike Christie
     [not found] ` <CGME20220308004023epcas2p12ebd497c14d32f36d0aa6682c0b9d0db@epcms2p7>
2022-03-08  7:00   ` [RFC PATCH 1/4] scsi: Allow drivers to set BLK_MQ_F_BLOCKING Daejun Park
2022-03-08 16:14     ` Mike Christie
2022-03-15  8:26 ` [RFC PATCH 0/4] scsi/iscsi: Send iscsi data from kblockd Christoph Hellwig
2022-03-16  1:08   ` Ming Lei

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