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Date: Thu, 25 Feb 2010 20:33:32 -0500
From: Rik van Riel <riel@redhat.com>
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To: Wu Fengguang <fengguang.wu@intel.com>
CC: Andrew Morton <akpm@linux-foundation.org>,
       Jens Axboe <jens.axboe@oracle.com>, Nick Piggin <npiggin@suse.de>,
       Chris Mason <chris.mason@oracle.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Clemens Ladisch <clemens@ladisch.de>,
       Olivier Galibert <galibert@pobox.com>, Vivek Goyal <vgoyal@redhat.com>,
       Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>,
       Matt Mackall <mpm@selenic.com>,
       Linux Memory Management List <linux-mm@kvack.org>,
       linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 15/15] readahead: pagecache context based mmap read-around
References: <20100224031001.026464755@intel.com> <20100224031055.738182009@intel.com>
In-Reply-To: <20100224031055.738182009@intel.com>
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On 02/23/2010 10:10 PM, Wu Fengguang wrote:
> Do mmap read-around when there are cached pages in the nearby 256KB
> (covered by one radix tree node).
>
> There is a failure case though: for a sequence of page faults at page
> index 64*i+1, i=1,2,3,..., this heuristic will keep doing pointless
> read-arounds.  Hopefully the pattern won't appear in real workloads.
> Note that the readahead heuristic has similiar failure case.
>
> CC: Nick Piggin<npiggin@suse.de>
> Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>

Acked-by: Rik van Riel <riel@redhat.com>