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

From: Mark Salyzyn
Date: Tue Sep 22 2015 - 10:15:10 EST


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
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