From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx204.postini.com [74.125.245.204]) by kanga.kvack.org (Postfix) with SMTP id 357FA6B004D for ; Mon, 19 Nov 2012 15:43:29 -0500 (EST) Date: Mon, 19 Nov 2012 12:43:27 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: cma: allocate pages from CMA if NR_FREE_PAGES approaches low water mark Message-Id: <20121119124327.20e008a0.akpm@linux-foundation.org> In-Reply-To: <50AA526A.7080505@samsung.com> References: <1352710782-25425-1-git-send-email-m.szyprowski@samsung.com> <20121114145848.8224e8b0.akpm@linux-foundation.org> <50AA526A.7080505@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Marek Szyprowski Cc: linux-mm@kvack.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, Kyungmin Park , Mel Gorman , Michal Nazarewicz , Minchan Kim , Bartlomiej Zolnierkiewicz On Mon, 19 Nov 2012 16:38:18 +0100 Marek Szyprowski wrote: > Hello, > > On 11/14/2012 11:58 PM, Andrew Morton wrote: > > On Mon, 12 Nov 2012 09:59:42 +0100 > > Marek Szyprowski wrote: > > > > > It has been observed that system tends to keep a lot of CMA free pages > > > even in very high memory pressure use cases. The CMA fallback for movable > > > pages is used very rarely, only when system is completely pruned from > > > MOVABLE pages, what usually means that the out-of-memory even will be > > > triggered very soon. To avoid such situation and make better use of CMA > > > pages, a heuristics is introduced which turns on CMA fallback for movable > > > pages when the real number of free pages (excluding CMA free pages) > > > approaches low water mark. > > ... > > > erk, this is right on the page allocator hotpath. Bad. > > Yes, I know that it adds an overhead to allocation hot path, but I found > no other > place for such change. Do You have any suggestion where such change can > be applied > to avoid additional load on hot path? Do the work somewhere else, not on a hot path? Somewhere on the page reclaim path sounds appropriate. How messy would it be to perform some sort of balancing at reclaim time? -- 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