From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id F1A0B6B0010 for ; Wed, 14 Sep 2011 23:35:30 -0400 (EDT) From: Satoru Moriya Date: Wed, 14 Sep 2011 23:33:34 -0400 Subject: Re: [PATCH -v2 -mm] add extra free kbytes tunable Message-ID: <65795E11DBF1E645A09CEC7EAEE94B9CAFE00221@USINDEVS02.corp.hds.com> References: <20110901105208.3849a8ff@annuminas.surriel.com> <20110901100650.6d884589.rdunlap@xenotime.net> <20110901152650.7a63cb8b@annuminas.surriel.com> <20110901145819.4031ef7c.akpm@linux-foundation.org>, In-Reply-To: Content-Language: ja-JP Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Rik van Riel Cc: Randy Dunlap , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "lwoodman@redhat.com" , Seiji Aguchi , "hughd@google.com" , "hannes@cmpxchg.org" On 09/02/2011 12:31 PM, Satoru Moriya wrote: > On 09/01/2011 05:58 PM, Andrew Morton wrote: >> On Thu, 1 Sep 2011 15:26:50 -0400 >> Rik van Riel wrote: > Anyway, now I'm testing this patch and will report a test result later. Sorry for late reply. Here is my test result. I ran some sample workloads and measure memory allocation latency (latency of __alloc_page_nodemask()). The test is like following: - CPU: 1 socket, 4 core - Memory: 4GB - Background load: $ dd if=3D/dev/zero of=3D/tmp/tmp1 $ dd if=3D/dev/zero of=3D/tmp/tmp2 $ dd if=3D/dev/zero of=3D/tmp/tmp3 - Main load: $ mapped-file-stream 1 $((1024 * 1024 * 640)) --(*) (*) This is made by Johannes Weiner https://lkml.org/lkml/2010/8/30/226 It allocates/access 640MByte memory at a burst. The result is follwoing: | | extra | | default | kbytes | -------------------------------------------------------------- min_free_kbytes | 8113 | 8113 | extra_free_kbytes | 0 | 640*1024 | (KB) -------------------------------------------------------------- worst latency | 517.762 | 20.775 | (usec) -------------------------------------------------------------- vmstat result | | | nr_vmscan_write | 0 | 0 | pgsteal_dma | 0 | 0 | pgsteal_dma32 | 143667 | 144882 | pgsteal_normal | 31486 | 27001 | pgsteal_movable | 0 | 0 | pgscan_kswapd_dma | 0 | 0 | pgscan_kswapd_dma32 | 138617 | 156351 | pgscan_kswapd_normal | 30593 | 27955 | pgscan_kswapd_movable | 0 | 0 | pgscan_direct_dma | 0 | 0 | pgscan_direct_dma32 | 5050 | 0 | pgscan_direct_normal | 896 | 0 | pgscan_direct_movable | 0 | 0 | kswapd_steal | 169207 | 171883 | kswapd_inodesteal | 0 | 0 | kswapd_low_wmark_hit_quickly | 43 | 45 | kswapd_high_wmark_hit_quickly | 1 | 0 | allocstall | 32 | 0 | As you can see, in the default case there were 32 direct reclaim (allocstal= l) and its worst latency was 517.762 usecs. This value may be larger if a process would sleep or issue I/O in the direct reclaim path. OTOH, ii the other case where I add extra free bytes, there were no direct reclaim and its worst latency was 20.775 usecs. In this test case, we can avoid direct reclaim and keep a latency low. Tested-by: Satoru Moriya -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org