Subject: ARM64 readahead: fault retry breaks mmap file read random detection

From: [email-masked] (Mark Salyzyn)
Date: Tue, 22 Sep 2015 07:15:00 -0700

On 09/21/2015 04:51 PM, Will Deacon wrote:
> 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
I see I am mistaken, arm64 was the _only_ one I see that is missing ... 
<grin>

Sincerely -- Mark Salyzyn