From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933610Ab0JSAmA (ORCPT ); Mon, 18 Oct 2010 20:42:00 -0400 Received: from smtp-out.google.com ([74.125.121.35]:58193 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933490Ab0JSAl7 (ORCPT ); Mon, 18 Oct 2010 20:41:59 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=wSyDJDxtDUT5qsUM52t2At2MMDvmdLmX00kSDXpeQLyri5j446J3DFduHXuNFxvrR 4ag0tPqr4OFJfUPRyzcsQ== From: Greg Thelen To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, containers@lists.osdl.org, Andrea Righi , Balbir Singh , KAMEZAWA Hiroyuki , Daisuke Nishimura , Minchan Kim , Ciju Rajan K , David Rientjes , Greg Thelen Subject: [PATCH v3 02/11] memcg: document cgroup dirty memory interfaces Date: Mon, 18 Oct 2010 17:39:35 -0700 Message-Id: <1287448784-25684-3-git-send-email-gthelen@google.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1287448784-25684-1-git-send-email-gthelen@google.com> References: <1287448784-25684-1-git-send-email-gthelen@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Document cgroup dirty memory interfaces and statistics. Signed-off-by: Andrea Righi Signed-off-by: Greg Thelen --- Changelog since v1: - Renamed "nfs"/"total_nfs" to "nfs_unstable"/"total_nfs_unstable" in per cgroup memory.stat to match /proc/meminfo. - Allow [kKmMgG] suffixes for newly created dirty limit value cgroupfs files. - Describe a situation where a cgroup can exceed its dirty limit. Documentation/cgroups/memory.txt | 60 ++++++++++++++++++++++++++++++++++++++ 1 files changed, 60 insertions(+), 0 deletions(-) diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index 7781857..02bbd6f 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -385,6 +385,10 @@ mapped_file - # of bytes of mapped file (includes tmpfs/shmem) pgpgin - # of pages paged in (equivalent to # of charging events). pgpgout - # of pages paged out (equivalent to # of uncharging events). swap - # of bytes of swap usage +dirty - # of bytes that are waiting to get written back to the disk. +writeback - # of bytes that are actively being written back to the disk. +nfs_unstable - # of bytes sent to the NFS server, but not yet committed to + the actual storage. inactive_anon - # of bytes of anonymous memory and swap cache memory on LRU list. active_anon - # of bytes of anonymous and swap cache memory on active @@ -453,6 +457,62 @@ memory under it will be reclaimed. You can reset failcnt by writing 0 to failcnt file. # echo 0 > .../memory.failcnt +5.5 dirty memory + +Control the maximum amount of dirty pages a cgroup can have at any given time. + +Limiting dirty memory is like fixing the max amount of dirty (hard to reclaim) +page cache used by a cgroup. So, in case of multiple cgroup writers, they will +not be able to consume more than their designated share of dirty pages and will +be forced to perform write-out if they cross that limit. + +The interface is equivalent to the procfs interface: /proc/sys/vm/dirty_*. It +is possible to configure a limit to trigger both a direct writeback or a +background writeback performed by per-bdi flusher threads. The root cgroup +memory.dirty_* control files are read-only and match the contents of +the /proc/sys/vm/dirty_* files. + +Per-cgroup dirty limits can be set using the following files in the cgroupfs: + +- memory.dirty_ratio: the amount of dirty memory (expressed as a percentage of + cgroup memory) at which a process generating dirty pages will itself start + writing out dirty data. + +- memory.dirty_limit_in_bytes: the amount of dirty memory (expressed in bytes) + in the cgroup at which a process generating dirty pages will start itself + writing out dirty data. Suffix (k, K, m, M, g, or G) can be used to indicate + that value is kilo, mega or gigabytes. + + Note: memory.dirty_limit_in_bytes is the counterpart of memory.dirty_ratio. + Only one of them may be specified at a time. When one is written it is + immediately taken into account to evaluate the dirty memory limits and the + other appears as 0 when read. + +- memory.dirty_background_ratio: the amount of dirty memory of the cgroup + (expressed as a percentage of cgroup memory) at which background writeback + kernel threads will start writing out dirty data. + +- memory.dirty_background_limit_in_bytes: the amount of dirty memory (expressed + in bytes) in the cgroup at which background writeback kernel threads will + start writing out dirty data. Suffix (k, K, m, M, g, or G) can be used to + indicate that value is kilo, mega or gigabytes. + + Note: memory.dirty_background_limit_in_bytes is the counterpart of + memory.dirty_background_ratio. Only one of them may be specified at a time. + When one is written it is immediately taken into account to evaluate the dirty + memory limits and the other appears as 0 when read. + +A cgroup may contain more dirty memory than its dirty limit. This is possible +because of the principle that the first cgroup to touch a page is charged for +it. Subsequent page counting events (dirty, writeback, nfs_unstable) are also +counted to the originally charged cgroup. + +Example: If page is allocated by a cgroup A task, then the page is charged to +cgroup A. If the page is later dirtied by a task in cgroup B, then the cgroup A +dirty count will be incremented. If cgroup A is over its dirty limit but cgroup +B is not, then dirtying a cgroup A page from a cgroup B task may push cgroup A +over its dirty limit without throttling the dirtying cgroup B task. + 6. Hierarchy support The memory controller supports a deep hierarchy and hierarchical accounting. -- 1.7.1