linux-kernel - Re: [RFC PATCH 0/6] Convert all tasklets to workqueues

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Date:	Thu, 28 Jun 2007 14:23:54 -0700
From:	"Dan Williams" <dan.j.williams@...el.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Christoph Hellwig" <hch@...radead.org>,
	"john stultz" <johnstul@...ibm.com>,
	"Oleg Nesterov" <oleg@...sign.ru>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Dipankar Sarma" <dipankar@...ibm.com>,
	"David S. Miller" <davem@...emloft.net>, kuznet@....inr.ac.ru,
	"Jeff Garzik" <jeff@...zik.org>
Subject: Re: [RFC PATCH 0/6] Convert all tasklets to workqueues

On 6/28/07, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Thu, 28 Jun 2007, Dan Williams wrote:
> > >
> > Unfortunately setting the thread to real time priority makes
> > throughput slightly worse.  Instead of floating around 35MB/s the
> > resync speed is stuck around 30MB/s:
>
> That is really strange. If you higher the prio of the work queue it
> gets worst?  Something really strange is happening here?  Are you using
> CONFIG_PREEMPT?
>
Everything thus far has been CONFIG_PREEMPT=n (the default for this platform).

With CONFIG_PREEMPT=y the resync is back in the 50MB/s range.

[iop-adma: hi-prio workqueue, CONFIG_PREEMPT=y]
iq81340mc:~# cat /proc/mdstat
Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md0 : active raid5 sdd[4] sdc[2] sdb[1] sda[0]
      468872448 blocks level 5, 64k chunk, algorithm 2 [4/3] [UUU_]
      [=>...................]  recovery =  5.8% (9136404/156290816)
finish=46.1min speed=53161K/sec

The tasklet configuration stays in 50MB/s ballpark, and the default
priority (nice -5) workqueue case remains in the 30's with
CONFIG_PREEMPT=n.

--
Dan
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