linux-kernel - Re: [PATCH] block_dev: implement readpages() to optimize sequential read

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Date:	Fri, 18 Jul 2014 08:14:03 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] block_dev: implement readpages() to optimize sequential read

2014-07-18 3:31 GMT+09:00 Jeff Moyer <jmoyer@...hat.com>:
> Akinobu Mita <akinobu.mita@...il.com> writes:
>
>> Sequential read from a block device is expected to be equal or faster
>> than from the file on a filesystem.  But it is not correct due to the
>> lack of effective readpages() in the address space operations for
>> block device.
>
> Ah, a trip down memory lane.  ;-)  Here's a thread showing issues with
> the last time this was proposed (by me, incidentally):
>
> https://lkml.org/lkml/2009/6/2/480
>
> At the very least, we need to see numbers on a real device, and see it
> booted on something with >4k page size before taking this back in.

Thanks for the information.  First, I'll try to reproduce the >4k page
size issue with qemu with the architecture which can support 64k page.
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