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Message-ID: <50EA8CA2.7020608@jp.fujitsu.com>
Date: Mon, 07 Jan 2013 17:51:46 +0900
From: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Anton Vorontsov <anton.vorontsov@...aro.org>
CC: David Rientjes <rientjes@...gle.com>,
Pekka Enberg <penberg@...nel.org>,
Mel Gorman <mgorman@...e.de>,
Glauber Costa <glommer@...allels.com>,
Michal Hocko <mhocko@...e.cz>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Luiz Capitulino <lcapitulino@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Greg Thelen <gthelen@...gle.com>,
Leonid Moiseichuk <leonid.moiseichuk@...ia.com>,
KOSAKI Motohiro <kosaki.motohiro@...il.com>,
Minchan Kim <minchan@...nel.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
John Stultz <john.stultz@...aro.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
patches@...aro.org, kernel-team@...roid.com
Subject: Re: [PATCH 1/2] Add mempressure cgroup
(2013/01/04 17:29), Anton Vorontsov wrote:
> This commit implements David Rientjes' idea of mempressure cgroup.
>
> The main characteristics are the same to what I've tried to add to vmevent
> API; internally, it uses Mel Gorman's idea of scanned/reclaimed ratio for
> pressure index calculation. But we don't expose the index to the userland.
> Instead, there are three levels of the pressure:
>
> o low (just reclaiming, e.g. caches are draining);
> o medium (allocation cost becomes high, e.g. swapping);
> o oom (about to oom very soon).
>
> The rationale behind exposing levels and not the raw pressure index
> described here: http://lkml.org/lkml/2012/11/16/675
>
> For a task it is possible to be in both cpusets, memcg and mempressure
> cgroups, so by rearranging the tasks it is possible to watch a specific
> pressure (i.e. caused by cpuset and/or memcg).
>
> Note that while this adds the cgroups support, the code is well separated
> and eventually we might add a lightweight, non-cgroups API, i.e. vmevent.
> But this is another story.
>
> Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
I'm just curious..
> ---
> Documentation/cgroups/mempressure.txt | 50 ++++++
> include/linux/cgroup_subsys.h | 6 +
> include/linux/vmstat.h | 11 ++
> init/Kconfig | 12 ++
> mm/Makefile | 1 +
> mm/mempressure.c | 330 ++++++++++++++++++++++++++++++++++
> mm/vmscan.c | 4 +
> 7 files changed, 414 insertions(+)
> create mode 100644 Documentation/cgroups/mempressure.txt
> create mode 100644 mm/mempressure.c
>
> diff --git a/Documentation/cgroups/mempressure.txt b/Documentation/cgroups/mempressure.txt
> new file mode 100644
> index 0000000..dbc0aca
> --- /dev/null
> +++ b/Documentation/cgroups/mempressure.txt
> @@ -0,0 +1,50 @@
> + Memory pressure cgroup
> +~~~~~~~~~~~~~~~~~~~~~~~~~~
> + Before using the mempressure cgroup, make sure you have it mounted:
> +
> + # cd /sys/fs/cgroup/
> + # mkdir mempressure
> + # mount -t cgroup cgroup ./mempressure -o mempressure
> +
> + It is possible to combine cgroups, for example you can mount memory
> + (memcg) and mempressure cgroups together:
> +
> + # mount -t cgroup cgroup ./mempressure -o memory,mempressure
> +
> + That way the reported pressure will honour memory cgroup limits. The
> + same goes for cpusets.
> +
> + After the hierarchy is mounted, you can use the following API:
> +
> + /sys/fs/cgroup/.../mempressure.level
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + To maintain the interactivity/memory allocation cost, one can use the
> + pressure level notifications, and the levels are defined like this:
> +
> + The "low" level means that the system is reclaiming memory for new
> + allocations. Monitoring reclaiming activity might be useful for
> + maintaining overall system's cache level. Upon notification, the program
> + (typically "Activity Manager") might analyze vmstat and act in advance
> + (i.e. prematurely shutdown unimportant services).
> +
> + The "medium" level means that the system is experiencing medium memory
> + pressure, there is some mild swapping activity. Upon this event
> + applications may decide to free any resources that can be easily
> + reconstructed or re-read from a disk.
> +
> + The "oom" level means that the system is actively thrashing, it is about
> + to out of memory (OOM) or even the in-kernel OOM killer is on its way to
> + trigger. Applications should do whatever they can to help the system.
> +
> + Event control:
> + Is used to setup an eventfd with a level threshold. The argument to
> + the event control specifies the level threshold.
> + Read:
> + Reads mempory presure levels: low, medium or oom.
> + Write:
> + Not implemented.
> + Test:
> + To set up a notification:
> +
> + # cgroup_event_listener ./mempressure.level low
> + ("low", "medium", "oom" are permitted.)
> diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
> index f204a7a..b9802e2 100644
> --- a/include/linux/cgroup_subsys.h
> +++ b/include/linux/cgroup_subsys.h
> @@ -37,6 +37,12 @@ SUBSYS(mem_cgroup)
>
> /* */
>
> +#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_MEMPRESSURE)
> +SUBSYS(mpc_cgroup)
> +#endif
> +
> +/* */
> +
> #if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEVICE)
> SUBSYS(devices)
> #endif
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index a13291f..c1a66c7 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -10,6 +10,17 @@
>
> extern int sysctl_stat_interval;
>
> +struct mem_cgroup;
> +#ifdef CONFIG_CGROUP_MEMPRESSURE
> +extern void vmpressure(struct mem_cgroup *memcg,
> + ulong scanned, ulong reclaimed);
> +extern void vmpressure_prio(struct mem_cgroup *memcg, int prio);
> +#else
> +static inline void vmpressure(struct mem_cgroup *memcg,
> + ulong scanned, ulong reclaimed) {}
> +static inline void vmpressure_prio(struct mem_cgroup *memcg, int prio) {}
> +#endif
> +
> #ifdef CONFIG_VM_EVENT_COUNTERS
> /*
> * Light weight per cpu counter implementation.
> diff --git a/init/Kconfig b/init/Kconfig
> index 7d30240..d526249 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -891,6 +891,18 @@ config MEMCG_KMEM
> the kmem extension can use it to guarantee that no group of processes
> will ever exhaust kernel resources alone.
>
> +config CGROUP_MEMPRESSURE
> + bool "Memory pressure monitor for Control Groups"
> + help
> + The memory pressure monitor cgroup provides a facility for
> + userland programs so that they could easily assist the kernel
> + with the memory management. So far the API provides simple,
> + levels-based memory pressure notifications.
> +
> + For more information see Documentation/cgroups/mempressure.txt
> +
> + If unsure, say N.
> +
> config CGROUP_HUGETLB
> bool "HugeTLB Resource Controller for Control Groups"
> depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
> diff --git a/mm/Makefile b/mm/Makefile
> index 3a46287..e69bbda 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -51,6 +51,7 @@ obj-$(CONFIG_MIGRATION) += migrate.o
> obj-$(CONFIG_QUICKLIST) += quicklist.o
> obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o
> obj-$(CONFIG_MEMCG) += memcontrol.o page_cgroup.o
> +obj-$(CONFIG_CGROUP_MEMPRESSURE) += mempressure.o
> obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o
> obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
> obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
> diff --git a/mm/mempressure.c b/mm/mempressure.c
> new file mode 100644
> index 0000000..ea312bb
> --- /dev/null
> +++ b/mm/mempressure.c
> @@ -0,0 +1,330 @@
> +/*
> + * Linux VM pressure
> + *
> + * Copyright 2012 Linaro Ltd.
> + * Anton Vorontsov <anton.vorontsov@...aro.org>
> + *
> + * Based on ideas from Andrew Morton, David Rientjes, KOSAKI Motohiro,
> + * Leonid Moiseichuk, Mel Gorman, Minchan Kim and Pekka Enberg.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published
> + * by the Free Software Foundation.
> + */
> +
> +#include <linux/cgroup.h>
> +#include <linux/fs.h>
> +#include <linux/sched.h>
> +#include <linux/mm.h>
> +#include <linux/vmstat.h>
> +#include <linux/eventfd.h>
> +#include <linux/swap.h>
> +#include <linux/printk.h>
> +
> +static void mpc_vmpressure(struct mem_cgroup *memcg, ulong s, ulong r);
> +
> +/*
> + * Generic VM Pressure routines (no cgroups or any other API details)
> + */
> +
> +/*
> + * The window size is the number of scanned pages before we try to analyze
> + * the scanned/reclaimed ratio (or difference).
> + *
> + * It is used as a rate-limit tunable for the "low" level notification,
> + * and for averaging medium/oom levels. Using small window sizes can cause
> + * lot of false positives, but too big window size will delay the
> + * notifications.
> + */
> +static const uint vmpressure_win = SWAP_CLUSTER_MAX * 16;
> +static const uint vmpressure_level_med = 60;
> +static const uint vmpressure_level_oom = 99;
> +static const uint vmpressure_level_oom_prio = 4;
> +
Hmm... isn't this window size too small ?
If vmscan cannot find a reclaimable page while scanning 2M of pages in a zone,
oom notify will be returned. Right ?
Thanks,
-Kame
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