linux-ext4 - Re: ext4 dbench performance with CONFIG_PREEMPT

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Message-ID: <20100410115816.GH1849@thunk.org>
Date:	Sat, 10 Apr 2010 07:58:16 -0400
From:	tytso@....edu
To:	"Chen, Tim C" <tim.c.chen@...el.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	john stultz <johnstul@...ibm.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Mingming Cao <cmm@...ibm.com>,
	keith maanthey <kmannth@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Darren Hart <dvhltc@...ibm.com>
Subject: Re: ext4 dbench performance with CONFIG_PREEMPT_RT

On Fri, Apr 09, 2010 at 05:48:23PM -0600, Chen, Tim C wrote:
>  
> Your patch did remove the contention on the j_state_lock for dbench
> in my testing with 64 threads.  The contention point now
> moves dcache_lock, which is also another tricky bottleneck.
> 
> In our other testing with FFSB that creates/rename/remove a lot of directories,
> we found that journal->j_revoke_lock was also heavily contended.
> 

Do you have lock_stat reports handy?  I'd love to take a look at them.

Thanks,

						- Ted
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