From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx153.postini.com [74.125.245.153]) by kanga.kvack.org (Postfix) with SMTP id 53ADC6B00B1 for ; Wed, 21 Nov 2012 10:01:58 -0500 (EST) Date: Wed, 21 Nov 2012 15:01:50 +0000 From: Mel Gorman Subject: Re: [RFC 3/3] man-pages: Add man page for vmpressure_fd(2) Message-ID: <20121121150149.GE8218@suse.de> References: <20121107105348.GA25549@lizard> <20121107110152.GC30462@lizard> <20121119215211.6370ac3b.akpm@linux-foundation.org> <20121120062400.GA9468@lizard> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Anton Vorontsov , Andrew Morton , Pekka Enberg , Leonid Moiseichuk , KOSAKI Motohiro , Minchan Kim , Bartlomiej Zolnierkiewicz , John Stultz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org, patches@linaro.org, kernel-team@android.com, linux-man@vger.kernel.org On Tue, Nov 20, 2012 at 10:12:28AM -0800, David Rientjes wrote: > On Mon, 19 Nov 2012, Anton Vorontsov wrote: > > > We try to make userland freeing resources when the system becomes low on > > memory. Once we're short on memory, sometimes it's better to discard > > (free) data, rather than let the kernel to drain file caches or even start > > swapping. > > > > To add another usecase: its possible to modify our version of malloc (or > any malloc) so that memory that is free()'d can be released back to the > kernel only when necessary, i.e. when keeping the extra memory around > starts to have a detremental effect on the system, memcg, or cpuset. When > there is an abundance of memory available such that allocations need not > defragment or reclaim memory to be allocated, it can improve performance > to keep a memory arena from which to allocate from immediately without > calling the kernel. > A potential third use case is a variation of the first for batch systems. If it's running low priority tasks and a high priority task starts that results in memory pressure then the job scheduler may decide to move the low priority jobs elsewhere (or cancel them entirely). A similar use case is monitoring systems running high priority workloads that should never swap. It can be easily detected if the system starts swapping but a pressure notification might act as an early warning system that something is happening on the system that might cause the primary workload to start swapping. -- 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