linux-kernel - Re: [PATCH V6 ] mm readahead: Fix readahead fail for memoryless cpu and limit readahead pages

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Message-ID: <5327F218.1000506@linux.vnet.ibm.com>
Date:	Tue, 18 Mar 2014 12:43:28 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Madper Xie <cxie@...hat.com>
CC:	Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	David Cohen <david.a.cohen@...ux.intel.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Damien Ramonda <damien.ramonda@...el.com>, rientjes@...gle.com,
	Linus <torvalds@...ux-foundation.org>, nacc@...ux.vnet.ibm.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 ] mm readahead: Fix readahead fail for memoryless cpu
 and limit readahead pages

On 03/17/2014 07:37 AM, Madper Xie wrote:
>
> Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> writes:
>
>> On 02/18/2014 03:19 PM, Jan Kara wrote:
>>> On Tue 18-02-14 12:55:38, Raghavendra K T wrote:
> Hi. Just a concern. Will the performance reduce on some special storage
> backend? E.g. tape.
> The existent applications may using readahead for userspace I/O schedule
> to decrease seeking time.

I have not tested the patch on such systems yet unfortunately :(.
Sequential read with huge file has not suffered on disk based system,
but I think, I should be honest enough not to guess the effect on tape.

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