From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx122.postini.com [74.125.245.122]) by kanga.kvack.org (Postfix) with SMTP id BAFDD6B0044 for ; Tue, 3 Apr 2012 07:25:28 -0400 (EDT) Message-ID: <4F7ADE1A.2050004@redhat.com> Date: Tue, 03 Apr 2012 13:25:14 +0200 From: Jerome Marchand MIME-Version: 1.0 Subject: Re: [RFC][PATCH] avoid swapping out with swappiness==0 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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: Satoru Moriya , "jweiner@redhat.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "riel@redhat.com" , "lwoodman@redhat.com" , "shaohua.li@intel.com" , "dle-develop@lists.sourceforge.net" , Seiji Aguchi 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=0 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 fail in this case. >> >> So the kernel reclaims pages like following. >> >> nr_free + nr_filebacked >= watermark_high: reclaim only filebacked pages >> nr_free + nr_filebacked < watermark_high: reclaim only anonymous pages > > How? get_scan_count() checks that case explicitly: if (global_reclaim(sc)) { free = zone_page_state(mz->zone, NR_FREE_PAGES); /* If we have very few page cache pages, force-scan anon pages. */ if (unlikely(file + free <= high_wmark_pages(mz->zone))) { fraction[0] = 1; fraction[1] = 0; denominator = 1; goto out; } } Regards, Jerome > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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