From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: [patch 1/2] mm: page-writeback: fix dirty_balance_reserve subtraction from dirtyable memory Date: Fri, 24 Jan 2014 18:05:09 -0500 Message-ID: <52E2F1A5.7010907@redhat.com> References: <1390600984-13925-1-git-send-email-hannes@cmpxchg.org> <1390600984-13925-2-git-send-email-hannes@cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Tejun Heo , Mel Gorman , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Johannes Weiner , Andrew Morton Return-path: In-Reply-To: <1390600984-13925-2-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On 01/24/2014 05:03 PM, Johannes Weiner wrote: > The dirty_balance_reserve is an approximation of the fraction of free > pages that the page allocator does not make available for page cache > allocations. As a result, it has to be taken into account when > calculating the amount of "dirtyable memory", the baseline to which > dirty_background_ratio and dirty_ratio are applied. > > However, currently the reserve is subtracted from the sum of free and > reclaimable pages, which is non-sensical and leads to erroneous > results when the system is dominated by unreclaimable pages and the > dirty_balance_reserve is bigger than free+reclaimable. In that case, > at least the already allocated cache should be considered dirtyable. > > Fix the calculation by subtracting the reserve from the amount of free > pages, then adding the reclaimable pages on top. > > Signed-off-by: Johannes Weiner Reviewed-by: Rik van Riel -- All rights reversed -- 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