linux-kernel - Re: [PATCH 1/3] IB/ehca: Replace vmalloc with kmalloc

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Date:	Tue, 28 Apr 2009 18:02:47 +0200
From:	Stefan Roscher <ossrosch@...ux.vnet.ibm.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	"LinuxPPC-Dev" <linuxppc-dev@...abs.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Roland Dreier <rolandd@...co.com>, fenkes@...ibm.com,
	raisch@...ibm.com, alexschm@...ibm.com, stefan.roscher@...ibm.com,
	hnguyen@...ibm.com
Subject: Re: [PATCH 1/3] IB/ehca: Replace vmalloc with kmalloc

On Tuesday 28 April 2009 05:12:51 pm Dave Hansen wrote:
> On Tue, 2009-04-21 at 17:16 +0200, Stefan Roscher wrote:
> > From: Anton Blanchard <antonb at au1.ibm.com>
> > 
> > To improve performance of driver ressource allocation,
> > replace the vmalloc() call with kmalloc().
> 
> Just curious, but how big are these allocations?  Why was vmalloc() even
> ever used if we know they'll be small?
> 
> -- Dave
> 
> 

The theoretical maximum size can be 512k, but for common queue pairs 
less than 128k is used.Because of the theoretical maximum we implemented
vmalloc() first, but recognized a huge performance impact.

-- Stefan 

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