From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: [PATCH 06/15] readahead: replace ra->mmap_miss with ra->ra_flags Date: Thu, 25 Feb 2010 10:52:28 -0500 Message-ID: <4B869CBC.5070501@redhat.com> References: <20100224031001.026464755@intel.com> <20100224031054.449606633@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Andrew Morton , Jens Axboe , Nick Piggin , Andi Kleen , Steven Whitehouse , Chris Mason , Peter Zijlstra , Clemens Ladisch , Olivier Galibert , Vivek Goyal , Christian Ehrhardt , Matt Mackall , Linux Memory Management List , linux-fsdevel@vger.kernel.org, LKML To: Wu Fengguang Return-path: In-Reply-To: <20100224031054.449606633@intel.com> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On 02/23/2010 10:10 PM, Wu Fengguang wrote: > Introduce a readahead flags field and embed the existing mmap_miss in it > (mainly to save space). > > It also changes the mmap_miss upper bound from LONG_MAX to 4096. > This is to help adapt properly for changing mmap access patterns. > > It will be possible to lose the flags in race conditions, however the > impact should be limited. For the race to happen, there must be two > threads sharing the same file descriptor to be in page fault or > readahead at the same time. > > Note that it has always been racy for "page faults" at the same time. > > And if ever the race happen, we'll lose one mmap_miss++ or mmap_miss--. > Which may change some concrete readahead behavior, but won't really > impact overall I/O performance. > > CC: Nick Piggin > CC: Andi Kleen > CC: Steven Whitehouse > Signed-off-by: Wu Fengguang Acked-by: Rik van Riel -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org