linux-kernel - Re: [PATCH] fs/proc: Move kfree outside pde_unload

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Date:	Fri, 24 Aug 2012 16:58:31 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Nathan Zimmer <nzimmer@....com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	adobriyan@...il.com, Alexander Viro <viro@...iv.linux.org.uk>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] fs/proc: Move kfree outside pde_unload_lock

Le vendredi 24 août 2012 à 09:48 -0500, Nathan Zimmer a écrit :
> On Wed, Aug 22, 2012 at 11:42:58PM +0200, Eric Dumazet wrote:
> > On Wed, 2012-08-22 at 20:28 +0200, Eric Dumazet wrote:
> > 
> > > 
> > > Thats interesting, but if you really want this to fly, one RCU
> > > conversion would be much better ;)
> > > 
> > > pde_users would be an atomic_t and you would avoid the spinlock
> > > contention.
> > 
> > Here is what I had in mind, I would be interested to know how it helps a 512 core machine ;)
> > 
> 
> Here are the results and they look great.
> 
> cpuinfo	baseline	moved kfree	Rcu 
> tasks	read-sec	read-sec	read-sec
> 1	0.0141		0.0141		0.0141
> 2	0.0140		0.0140		0.0142
> 4	0.0140		0.0141		0.0141
> 8	0.0145		0.0145		0.0140
> 16	0.0553		0.0548		0.0168
> 32	0.1688		0.1622		0.0549
> 64	0.5017		0.3856		0.1690
> 128	1.7005		0.9710		0.5038
> 256	5.2513		2.6519		2.0804
> 512	8.0529		6.2976		3.0162
> 
> 
> 

Indeed...

Could you explicit the test you are actually doing ?

Thanks


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