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Date: Tue, 18 Mar 2014 12:43:28 +0530
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Organization: IBM
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To: Madper Xie <cxie@redhat.com>
CC: Jan Kara <jack@suse.cz>, Andrew Morton <akpm@linux-foundation.org>,
        Fengguang Wu <fengguang.wu@intel.com>,
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        Linus <torvalds@linux-foundation.org>, nacc@linux.vnet.ibm.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V6 ] mm readahead: Fix readahead fail for memoryless cpu
 and limit readahead pages
References: <1392708338-19685-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140218094920.GB29660@quack.suse.cz> <53034C66.90707@linux.vnet.ibm.com> <871ty1zig4.fsf@redhat.com>
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On 03/17/2014 07:37 AM, Madper Xie wrote:
>
> Raghavendra K T <raghavendra.kt@linux.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.