From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx112.postini.com [74.125.245.112]) by kanga.kvack.org (Postfix) with SMTP id F26A56B0069 for ; Thu, 13 Dec 2012 06:21:02 -0500 (EST) Date: Thu, 13 Dec 2012 11:20:58 +0000 From: Mel Gorman Subject: Re: [PATCH v3] mm: Use aligned zone start for pfn_to_bitidx calculation Message-ID: <20121213112058.GA9887@suse.de> References: <1354828301-27849-1-git-send-email-lauraa@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1354828301-27849-1-git-send-email-lauraa@codeaurora.org> Sender: owner-linux-mm@kvack.org List-ID: To: Laura Abbott Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org On Thu, Dec 06, 2012 at 01:11:41PM -0800, Laura Abbott wrote: > The current calculation in pfn_to_bitidx assumes that > (pfn - zone->zone_start_pfn) >> pageblock_order will return the > same bit for all pfn in a pageblock. If zone_start_pfn is not > aligned to pageblock_nr_pages, this may not always be correct. > > Consider the following with pageblock order = 10, zone start 2MB: > > pfn | pfn - zone start | (pfn - zone start) >> page block order > ---------------------------------------------------------------- > 0x26000 | 0x25e00 | 0x97 > 0x26100 | 0x25f00 | 0x97 > 0x26200 | 0x26000 | 0x98 > 0x26300 | 0x26100 | 0x98 > > This means that calling {get,set}_pageblock_migratetype on a single > page will not set the migratetype for the full block. Fix this by > rounding down zone_start_pfn when doing the bitidx calculation. > > Signed-off-by: Laura Abbott Acked-by: Mel Gorman It's merge window at the moment so it's in danger of getting lost. What I suggest you do is do is resend to Andrew with the same people cc'd post-merge window so it'll be picked up in mmotm for the next cycle. Thanks. -- Mel Gorman SUSE Labs -- 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