linux-kernel - Re: ARM64 readahead: fault retry breaks mmap file read random detection

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Date:	Tue, 22 Sep 2015 00:51:20 +0100
From:	Will Deacon <will.deacon@....com>
To:	Mark Salyzyn <salyzyn@...roid.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Riley Andrews <riandrews@...roid.com>,
	Shaohua Li <shli@...nel.org>,
	Shaohua Li <shaohua.li@...ionio.com>,
	Rik van Riel <riel@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Vladimir Murzin <Vladimir.Murzin@....com>,
	Dave P Martin <Dave.Martin@....com>,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	James Morse <James.Morse@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: ARM64 readahead: fault retry breaks mmap file read random
 detection

On Mon, Sep 21, 2015 at 10:36:40PM +0100, Mark Salyzyn wrote:
> On 09/21/2015 02:09 PM, Will Deacon wrote:
> > On Mon, Sep 21, 2015 at 09:39:50PM +0100, Mark Salyzyn wrote:
> >> Description from commit 45cac65b0fcd
> >>      ("readahead: fault retry breaks mmap file read random detection")
> >> . . .
> >> Yup, arm64 needs this too! Random read improves by 250%, sequential
> >> read improves by 40%, and random write by 400% to an eMMC device with
> >> dm crypto wrapped around it.
> > Thanks for this. This must've gone in whilst we were developing the initial
> > version of the arm64 port and has since gone unnoticed.
> >
> > I'll queue it on the arm64 fixes branch and send a pull request after
> > some testing.
> >
> As noted, this fix may need to be propagated to all the arch-specific 
> code, I was not in a position to check this out on arm (32 bit) and the 
> benchmarking code I used did not immediately port to 32-bit.

You lost me; which arch-specific code are you referring to? The original
patch (in mainline) touches a whole bunch of architectures.

Will
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