linux-kernel - Re: scsi-mq

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Message-ID: <20140623070951.GB12267@lst.de>
Date:	Mon, 23 Jun 2014 09:09:51 +0200
From:	Christoph Hellwig <hch@....de>
To:	"Elliott, Robert (Server Storage)" <Elliott@...com>
Cc:	Bart Van Assche <bvanassche@....org>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: scsi-mq

On Sat, Jun 21, 2014 at 12:52:22AM +0000, Elliott, Robert (Server Storage) wrote:
> Some of those context switches might be from scsi_end_request(), 
> which always schedules the scsi_requeue_run_queue() function via the
> requeue_work workqueue for scsi-mq.  That causes lots of context 
> switches from a busy application thread (e.g., fio) to a 
> kworker thread.

Jens has been prodding me to fix this up, I'll send a patch soon that avoids
the workqueue unless we need to kick other queues and thus walk the list
of LUNs.

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