From: Bill Davidsen <davidsen@tmr.com>
To: Jordan Russell <jr-list-2010@quo.to>
Cc: linux-raid@vger.kernel.org
Subject: Re: Data-check brings system to a standstill
Date: Tue, 22 Jun 2010 14:50:38 -0400 [thread overview]
Message-ID: <4C2105FE.8020201@tmr.com> (raw)
In-Reply-To: <4C2036CB.7090505@quo.to>
Jordan Russell wrote:
> On 6/16/2010 11:52 AM, Bill Davidsen wrote:
>
>> Alternatively, you can try setting your io scheduler to
>> deadline,
>>
>
> Wow - huge difference! No "hung task" warnings, no processes stuck in
> "D" state; the system remains completely responsive throughout the
> entire check.
>
> I don't see why, though, processes are blocking for 2+ minutes on the
> simplest of I/O operations when the default CFQ scheduler is used. Isn't
> CFQ supposed to distribute I/O bandwidth in a "completely fair" manner?
> Do md checks bypass the fairness algorithm?
>
>
The CFQ has its own idea of what is "fair" and works poorly (even
abysmally as you saw) for some load cases.
--
Bill Davidsen <davidsen@tmr.com>
"We can't solve today's problems by using the same thinking we
used in creating them." - Einstein
prev parent reply other threads:[~2010-06-22 18:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-09 17:30 Data-check brings system to a standstill Jordan Russell
2010-06-16 16:52 ` Bill Davidsen
2010-06-18 16:54 ` Jordan Russell
2010-06-18 17:10 ` Tim Small
2010-06-18 17:27 ` Jordan Russell
2010-06-22 4:06 ` Jordan Russell
2010-06-22 18:50 ` Bill Davidsen [this message]
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