From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx147.postini.com [74.125.245.147]) by kanga.kvack.org (Postfix) with SMTP id 6DA8A6B0044 for ; Tue, 3 Apr 2012 11:17:56 -0400 (EDT) From: Satoru Moriya Date: Tue, 3 Apr 2012 11:15:30 -0400 Subject: RE: [RFC][PATCH] avoid swapping out with swappiness==0 Message-ID: <65795E11DBF1E645A09CEC7EAEE94B9C014536F9A3@USINDEVS02.corp.hds.com> References: <65795E11DBF1E645A09CEC7EAEE94B9CB9455FE2@USINDEVS02.corp.hds.com> <20120305215602.GA1693@redhat.com> <4F5798B1.5070005@jp.fujitsu.com> <65795E11DBF1E645A09CEC7EAEE94B9CB951A45F@USINDEVS02.corp.hds.com> <65795E11DBF1E645A09CEC7EAEE94B9C01454D13A6@USINDEVS02.corp.hds.com> ,<4F7ADE1A.2050004@redhat.com> In-Reply-To: <4F7ADE1A.2050004@redhat.com> 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: Jerome Marchand , KOSAKI Motohiro Cc: "jweiner@redhat.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "riel@redhat.com" , "lwoodman@redhat.com" , "dle-develop@lists.sourceforge.net" , Seiji Aguchi On 04/03/2012 07:25 AM, Jerome Marchand wrote: > On 04/02/2012 07:10 PM, KOSAKI Motohiro wrote: >> 2012/3/30 Satoru Moriya : >>> Hello Kosaki-san, >>> >>> On 03/07/2012 01:18 PM, Satoru Moriya wrote: >>>> On 03/07/2012 12:19 PM, KOSAKI Motohiro wrote: >>>>> Thank you. I brought back to memory it. Unfortunately DB folks are >>>>> still mainly using RHEL5 generation distros. At that time, >>>>> swapiness=3D0 doesn't mean disabling swap. >>>>> >>>>> They want, "don't swap as far as kernel has any file cache page". but >>>>> linux don't have such feature. then they used swappiness for emulate >>>>> it. So, I think this patch clearly make userland harm. Because of, we >>>>> don't have an alternative way. >>> >>> As I wrote in the previous mail(see below), with this patch >>> the kernel begins to swap out when the sum of free pages and >>> filebacked pages reduces less than watermark_high. > > Actually, this is true only for global reclaims. Reclaims in cgroup can f= ail > in this case. Right. As long as we consider RHEL5 users above, I believe they don't care about cgroup case. >>> >>> So the kernel reclaims pages like following. >>> >>> nr_free + nr_filebacked >=3D watermark_high: reclaim only filebacked pa= ges >>> nr_free + nr_filebacked < watermark_high: reclaim only anonymous pages I made a tiny mistake. Correct one is following ;p nr_free + nr_filebacked > watermark_high: reclaim only filebacked pages nr_free + nr_filebacked <=3D watermark_high: reclaim only anonymous pages >> How? > > get_scan_count() checks that case explicitly: > > if (global_reclaim(sc)) { > free =3D zone_page_state(mz->zone, NR_FREE_PAGES); > /* If we have very few page cache pages, > force-scan anon pages. */ > if (unlikely(file + free <=3D high_wmark_pages(mz->zone)))= { > fraction[0] =3D 1; > fraction[1] =3D 0; > denominator =3D 1; > goto out; > } > } Regards, Satoru= -- 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