From: Satoru Moriya <satoru.moriya@hds.com> To: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Randy Dunlap <rdunlap@xenotime.net>, Satoru Moriya <smoriya@redhat.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "lwoodman@redhat.com" <lwoodman@redhat.com>, Seiji Aguchi <saguchi@redhat.com>, "hughd@google.com" <hughd@google.com>, "hannes@cmpxchg.org" <hannes@cmpxchg.org> Subject: RE: [PATCH -v2 -mm] add extra free kbytes tunable Date: Wed, 26 Oct 2011 14:59:17 -0400 [thread overview] Message-ID: <65795E11DBF1E645A09CEC7EAEE94B9CB4F747B4@USINDEVS02.corp.hds.com> (raw) In-Reply-To: <alpine.DEB.2.00.1110251446340.26017@chino.kir.corp.google.com> emaOn 10/25/2011 05:50 PM, David Rientjes wrote: > On Mon, 24 Oct 2011, Satoru Moriya wrote: > >>>> We do. >>>> Basically we need this kind of feature for almost all our latency >>>> sensitive applications to avoid latency issue in memory allocation. >>> >>> These are all realtime? >> >> Do you mean that these are all realtime process? >> >> If so, answer is depending on the situation. In the some situations, >> we can set these applications as rt-task. But the other situation, >> e.g. using some middlewares, package softwares etc, we can't set them >> as rt-task because they are not built for running as rt-task. And also >> it is difficult to rebuilt them for working as rt-task because they >> usually have huge code base. >> > > If this problem affects processes that aren't realtime, then your only > option is to increase /proc/sys/vm/min_free_kbytes. It's unreasonable to > believe that the VM should be able to reclaim in the background at the > same rate that an application is allocating huge amounts of memory without > allowing there to be a buffer. Adding another tunable isn't going to > address that situation better than min_free_kbytes. Even if allocating memory in user space causes latency issues, usually allocation itself doesn't continue for a long time. Therefore if we can keep enough free memory, we can avoid latency issue in this situation. min_free_kbytes makes min wmark bigger too. It means that the amount of memory user processes can use without penalty(direct reclaim) decrease unnecessarily, this is what we'd like to avoid. >> As I reported another mail, changing kswapd priority does not mitigate >> even my simple testcase very much. Of course, reclaiming above the high >> wmark may solve the issue on some workloads but if an application can >> allocate memory more than high wmark - min wmark which is extended and >> fast enough, latency issue will happen. >> Unless this latency concern is fixed, customers doesn't use vanilla >> kernel. >> > And you have yet to provide an expression that shows what a sane setting > for this tunable will be. In fact, it seems like you're just doing trial > and error and finding where it works pretty well for a certain VM > implementation in a certain kernel. That's simply not a maintainable > userspace interface! Try and error is tuning itself. When we tune a system, we usually set some knobs, run some benchmarks/tests/etc., evaluate results and decide which is the best configuration. Regards, Satoru
WARNING: multiple messages have this Message-ID (diff)
From: Satoru Moriya <satoru.moriya@hds.com> To: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Randy Dunlap <rdunlap@xenotime.net>, Satoru Moriya <smoriya@redhat.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "lwoodman@redhat.com" <lwoodman@redhat.com>, Seiji Aguchi <saguchi@redhat.com>, "hughd@google.com" <hughd@google.com>, "hannes@cmpxchg.org" <hannes@cmpxchg.org> Subject: RE: [PATCH -v2 -mm] add extra free kbytes tunable Date: Wed, 26 Oct 2011 14:59:17 -0400 [thread overview] Message-ID: <65795E11DBF1E645A09CEC7EAEE94B9CB4F747B4@USINDEVS02.corp.hds.com> (raw) In-Reply-To: <alpine.DEB.2.00.1110251446340.26017@chino.kir.corp.google.com> emaOn 10/25/2011 05:50 PM, David Rientjes wrote: > On Mon, 24 Oct 2011, Satoru Moriya wrote: > >>>> We do. >>>> Basically we need this kind of feature for almost all our latency >>>> sensitive applications to avoid latency issue in memory allocation. >>> >>> These are all realtime? >> >> Do you mean that these are all realtime process? >> >> If so, answer is depending on the situation. In the some situations, >> we can set these applications as rt-task. But the other situation, >> e.g. using some middlewares, package softwares etc, we can't set them >> as rt-task because they are not built for running as rt-task. And also >> it is difficult to rebuilt them for working as rt-task because they >> usually have huge code base. >> > > If this problem affects processes that aren't realtime, then your only > option is to increase /proc/sys/vm/min_free_kbytes. It's unreasonable to > believe that the VM should be able to reclaim in the background at the > same rate that an application is allocating huge amounts of memory without > allowing there to be a buffer. Adding another tunable isn't going to > address that situation better than min_free_kbytes. Even if allocating memory in user space causes latency issues, usually allocation itself doesn't continue for a long time. Therefore if we can keep enough free memory, we can avoid latency issue in this situation. min_free_kbytes makes min wmark bigger too. It means that the amount of memory user processes can use without penalty(direct reclaim) decrease unnecessarily, this is what we'd like to avoid. >> As I reported another mail, changing kswapd priority does not mitigate >> even my simple testcase very much. Of course, reclaiming above the high >> wmark may solve the issue on some workloads but if an application can >> allocate memory more than high wmark - min wmark which is extended and >> fast enough, latency issue will happen. >> Unless this latency concern is fixed, customers doesn't use vanilla >> kernel. >> > And you have yet to provide an expression that shows what a sane setting > for this tunable will be. In fact, it seems like you're just doing trial > and error and finding where it works pretty well for a certain VM > implementation in a certain kernel. That's simply not a maintainable > userspace interface! Try and error is tuning itself. When we tune a system, we usually set some knobs, run some benchmarks/tests/etc., evaluate results and decide which is the best configuration. 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-10-26 19:00 UTC|newest] Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-09-01 14:52 [PATCH -mm] add extra free kbytes tunable Rik van Riel 2011-09-01 14:52 ` Rik van Riel 2011-09-01 17:06 ` Randy Dunlap 2011-09-01 17:06 ` Randy Dunlap 2011-09-01 19:26 ` [PATCH -v2 " Rik van Riel 2011-09-01 19:26 ` Rik van Riel 2011-09-01 21:58 ` Andrew Morton 2011-09-01 21:58 ` Andrew Morton 2011-09-01 22:08 ` David Rientjes 2011-09-01 22:08 ` David Rientjes 2011-09-01 22:16 ` Andrew Morton 2011-09-01 22:16 ` Andrew Morton 2011-09-02 16:31 ` Satoru Moriya 2011-09-02 16:31 ` Satoru Moriya 2011-10-13 7:33 ` Minchan Kim 2011-10-13 7:33 ` Minchan Kim 2011-10-13 8:09 ` KAMEZAWA Hiroyuki 2011-10-13 8:09 ` KAMEZAWA Hiroyuki [not found] ` <E1FA588BC672D846BDBB452FCA1E308C2389B4@USINDEVS02.corp.hds.com> 2011-09-15 3:33 ` Satoru Moriya 2011-09-15 3:33 ` Satoru Moriya 2011-09-01 22:09 ` Andrew Morton 2011-09-01 22:09 ` Andrew Morton 2011-09-02 16:26 ` [PATCH -mm] fixes & cleanups for "add extra free kbytes tunable" Rik van Riel 2011-09-02 16:26 ` Rik van Riel 2011-09-30 21:43 ` [PATCH -v2 -mm] add extra free kbytes tunable Johannes Weiner 2011-09-30 21:43 ` Johannes Weiner 2011-10-08 3:08 ` David Rientjes 2011-10-08 3:08 ` David Rientjes 2011-10-10 22:37 ` Andrew Morton 2011-10-10 22:37 ` Andrew Morton 2011-10-11 19:32 ` Satoru Moriya 2011-10-11 19:32 ` Satoru Moriya 2011-10-11 19:54 ` Andrew Morton 2011-10-11 19:54 ` Andrew Morton 2011-10-11 20:23 ` Satoru Moriya 2011-10-11 20:23 ` Satoru Moriya 2011-10-11 20:54 ` Andrew Morton 2011-10-11 20:54 ` Andrew Morton 2011-10-12 13:09 ` Rik van Riel 2011-10-12 13:09 ` Rik van Riel 2011-10-12 19:20 ` Andrew Morton 2011-10-12 19:20 ` Andrew Morton 2011-10-12 19:58 ` Rik van Riel 2011-10-12 19:58 ` Rik van Riel 2011-10-12 20:26 ` David Rientjes 2011-10-12 20:26 ` David Rientjes 2011-10-21 23:48 ` Satoru Moriya 2011-10-21 23:48 ` Satoru Moriya 2011-10-23 21:22 ` David Rientjes 2011-10-23 21:22 ` David Rientjes 2011-10-25 2:04 ` Satoru Moriya 2011-10-25 2:04 ` Satoru Moriya 2011-10-25 21:50 ` David Rientjes 2011-10-25 21:50 ` David Rientjes 2011-10-26 18:59 ` Satoru Moriya [this message] 2011-10-26 18:59 ` Satoru Moriya 2011-10-12 21:08 ` Satoru Moriya 2011-10-12 21:08 ` Satoru Moriya 2011-10-12 22:41 ` David Rientjes 2011-10-12 22:41 ` David Rientjes 2011-10-12 23:52 ` Satoru Moriya 2011-10-12 23:52 ` Satoru Moriya 2011-10-13 0:01 ` David Rientjes 2011-10-13 0:01 ` David Rientjes 2011-10-13 5:35 ` KAMEZAWA Hiroyuki 2011-10-13 5:35 ` KAMEZAWA Hiroyuki 2011-10-13 20:55 ` David Rientjes 2011-10-13 20:55 ` David Rientjes 2011-10-14 22:16 ` Satoru Moriya 2011-10-14 22:16 ` Satoru Moriya 2011-10-14 22:46 ` David Rientjes 2011-10-14 22:46 ` David Rientjes 2011-10-14 5:32 ` Satoru Moriya 2011-10-14 5:32 ` Satoru Moriya 2011-10-14 5:06 ` Satoru Moriya 2011-10-14 5:06 ` Satoru Moriya 2011-10-11 23:22 ` David Rientjes 2011-10-11 23:22 ` David Rientjes 2011-10-13 16:54 ` Satoru Moriya 2011-10-13 16:54 ` Satoru Moriya 2011-10-13 20:48 ` David Rientjes 2011-10-13 20:48 ` David Rientjes 2011-10-13 21:11 ` Rik van Riel 2011-10-13 21:11 ` Rik van Riel 2011-10-13 22:02 ` David Rientjes 2011-10-13 22:02 ` David Rientjes 2011-10-11 19:20 ` Satoru Moriya 2011-10-11 19:20 ` Satoru Moriya 2011-10-11 21:04 ` David Rientjes 2011-10-11 21:04 ` David Rientjes 2011-10-12 13:13 ` Rik van Riel 2011-10-12 13:13 ` Rik van Riel 2011-10-12 20:21 ` David Rientjes 2011-10-12 20:21 ` David Rientjes 2011-10-13 4:13 ` Rik van Riel 2011-10-13 4:13 ` Rik van Riel 2011-10-13 5:22 ` David Rientjes 2011-10-13 5:22 ` David Rientjes 2011-10-22 0:11 ` Satoru Moriya 2011-10-22 0:11 ` Satoru Moriya 2011-09-09 23:01 Satoru Moriya 2011-09-09 23:01 ` Satoru Moriya
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