Linux-Fsdevel Archive on lore.kernel.org
 help / color / Atom feed
From: Jonathan Corbet <corbet@lwn.net>
To: 王贇 <yun.wang@linux.alibaba.com>
Cc: "Ingo Molnar" <mingo@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Juri Lelli" <juri.lelli@redhat.com>,
	"Vincent Guittot" <vincent.guittot@linaro.org>,
	"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
	"Luis Chamberlain" <mcgrof@kernel.org>,
	"Kees Cook" <keescook@chromium.org>,
	"Iurii Zaikin" <yzaikin@google.com>,
	"Michal Koutný" <mkoutny@suse.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org,
	"Paul E. McKenney" <paulmck@linux.ibm.com>
Subject: Re: [PATCH 3/3] sched/numa: documentation for per-cgroup numa stat
Date: Wed, 13 Nov 2019 08:09:12 -0700
Message-ID: <20191113080912.041918ce@lwn.net> (raw)
In-Reply-To: <896a7da3-f139-32e7-8a64-b3562df1a091@linux.alibaba.com>

On Wed, 13 Nov 2019 11:45:59 +0800
王贇 <yun.wang@linux.alibaba.com> wrote:

> Add the description for 'cg_numa_stat', also a new doc to explain
> the details on how to deal with the per-cgroup numa statistics.
> 
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Michal Koutný <mkoutny@suse.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
> ---
>  Documentation/admin-guide/cg-numa-stat.rst      | 161 ++++++++++++++++++++++++
>  Documentation/admin-guide/kernel-parameters.txt |   4 +
>  Documentation/admin-guide/sysctl/kernel.rst     |   9 ++
>  3 files changed, 174 insertions(+)
>  create mode 100644 Documentation/admin-guide/cg-numa-stat.rst

Thanks for adding documentation for your new feature!  When you add a new
RST file, though, you should also add it to index.rst so that it becomes a
part of the docs build.

A couple of nits below...

> diff --git a/Documentation/admin-guide/cg-numa-stat.rst b/Documentation/admin-guide/cg-numa-stat.rst
> new file mode 100644
> index 000000000000..87b716c51e16
> --- /dev/null
> +++ b/Documentation/admin-guide/cg-numa-stat.rst
> @@ -0,0 +1,161 @@
> +===============================
> +Per-cgroup NUMA statistics
> +===============================
> +
> +Background
> +----------
> +
> +On NUMA platforms, remote memory accessing always has a performance penalty,
> +although we have NUMA balancing working hard to maximum the local accessing
> +proportion, there are still situations it can't helps.
> +
> +This could happen in modern production environment, using bunch of cgroups
> +to classify and control resources which introduced complex configuration on
> +memory policy, CPUs and NUMA node, NUMA balancing could facing the wrong
> +memory policy or exhausted local NUMA node, lead into the low local page
> +accessing proportion.
> +
> +We need to perceive such cases, figure out which workloads from which cgroup
> +has introduced the issues, then we got chance to do adjustment to avoid
> +performance damages.
> +
> +However, there are no hardware counter for per-task local/remote accessing
> +info, we don't know how many remote page accessing has been done for a
> +particular task.
> +
> +Statistics
> +----------
> +
> +Fortunately, we have NUMA Balancing which scan task's mapping and trigger PF
> +periodically, give us the opportunity to record per-task page accessing info.
> +
> +By "echo 1 > /proc/sys/kernel/cg_numa_stat" on runtime or add boot parameter
> +'cg_numa_stat', we will enable the accounting of per-cgroup numa statistics,
> +the 'cpu.numa_stat' entry of CPU cgroup will show statistics:
> +
> +  locality -- execution time sectioned by task NUMA locality (in ms)
> +  exectime -- execution time sectioned by NUMA node (in ms)
> +
> +We define 'task NUMA locality' as:
> +
> +  nr_local_page_access * 100 / (nr_local_page_access + nr_remote_page_access)
> +
> +this per-task percentage value will be updated on the ticks for current task,
> +and the access counter will be updated on task's NUMA balancing PF, so only
> +the pages which NUMA Balancing paid attention to will be accounted.
> +
> +On each tick, we acquire the locality of current task on that CPU, accumulating
> +the ticks into the counter of corresponding locality region, tasks from the
> +same group sharing the counters, becoming the group locality.
> +
> +Similarly, we acquire the NUMA node of current CPU where the current task is
> +executing on, accumulating the ticks into the counter of corresponding node,
> +becoming the per-cgroup node execution time.
> +
> +To be noticed, the accounting is in a hierarchy way, which means the numa
> +statistics representing not only the workload of this group, but also the
> +workloads of all it's descendants.
> +
> +For example the 'cpu.numa_stat' show:
> +  locality 39541 60962 36842 72519 118605 721778 946553
> +  exectime 1220127 1458684

You almost certainly want that rendered as a literal block, so say
"show::".  There are other places where you'll want to do that as well. 

> +The locality is sectioned into 7 regions, closely as:
> +  0-13% 14-27% 28-42% 43-56% 57-71% 72-85% 86-100%
> +
> +And exectime is sectioned into 2 nodes, 0 and 1 in this case.
> +
> +Thus we know the workload of this group and it's descendants have totally
> +executed 1220127ms on node_0 and 1458684ms on node_1, tasks with locality
> +around 0~13% executed for 39541 ms, and tasks with locality around 87~100%
> +executed for 946553 ms, which imply most of the memory access are local.
> +
> +Monitoring
> +-----------------

A slightly long underline :)

I'll stop here; thanks again for adding documentation.

jon

  reply index

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-13  3:43 [PATCH 0/3] sched/numa: introduce advanced numa statistic 王贇
2019-11-13  3:44 ` [PATCH 1/3] sched/numa: advanced per-cgroup " 王贇
2019-11-13  3:45 ` [PATCH 2/3] sched/numa: expose per-task pages-migration-failure 王贇
2019-11-13  3:45 ` [PATCH 3/3] sched/numa: documentation for per-cgroup numa stat 王贇
2019-11-13 15:09   ` Jonathan Corbet [this message]
2019-11-14  1:52     ` 王贇
2019-11-13 18:28   ` Iurii Zaikin
2019-11-14  2:22     ` 王贇
2019-11-15  2:29   ` [PATCH v2 " 王贇
2019-11-20  9:45 ` [PATCH 0/3] sched/numa: introduce advanced numa statistic 王贇
2019-11-25  1:35 ` 王贇
2019-11-27  1:48 ` [PATCH v2 " 王贇
2019-11-27  1:49   ` [PATCH v2 1/3] sched/numa: advanced per-cgroup " 王贇
2019-11-27 10:19     ` Mel Gorman
2019-11-28  2:09       ` 王贇
2019-11-28 12:39         ` Michal Koutný
2019-11-28 13:41           ` 王贇
2019-11-28 15:58             ` Michal Koutný
2019-11-29  1:52               ` 王贇
2019-11-29  5:19                 ` 王贇
2019-11-29 10:06                   ` Michal Koutný
2019-12-02  2:11                     ` 王贇
2019-11-27  1:50   ` [PATCH v2 2/3] sched/numa: expose per-task pages-migration-failure 王贇
2019-11-27 10:00     ` Mel Gorman
2019-12-02  2:22     ` 王贇
2019-11-27  1:50   ` [PATCH v2 3/3] sched/numa: documentation for per-cgroup numa stat 王贇
2019-11-27  4:58     ` Randy Dunlap
2019-11-27  5:54       ` 王贇
2019-12-03  5:59   ` [PATCH v3 0/2] sched/numa: introduce numa locality 王贇
2019-12-03  6:00     ` [PATCH v3 1/2] sched/numa: introduce per-cgroup NUMA locality info 王贇
2019-12-04  2:33       ` Randy Dunlap
2019-12-04  2:38         ` 王贇
2019-12-03  6:02     ` [PATCH v3 2/2] sched/numa: documentation for per-cgroup numa statistics 王贇
2019-12-03 13:43       ` Jonathan Corbet
2019-12-04  2:27         ` 王贇
2019-12-04  7:58     ` [PATCH v4 0/2] sched/numa: introduce numa locality 王贇
2019-12-04  7:59       ` [PATCH v4 1/2] sched/numa: introduce per-cgroup NUMA locality info 王贇
2019-12-05  3:28         ` Randy Dunlap
2019-12-05  3:29           ` Randy Dunlap
2019-12-05  3:52             ` 王贇
2019-12-04  8:00       ` [PATCH v4 2/2] sched/numa: documentation for per-cgroup numa statistics 王贇
2019-12-05  3:40         ` Randy Dunlap
2019-12-05  6:53       ` [PATCH v5 0/2] sched/numa: introduce numa locality 王贇
2019-12-05  6:53         ` [PATCH v5 1/2] sched/numa: introduce per-cgroup NUMA locality info 王贇
2019-12-05  6:54         ` [PATCH v5 2/2] sched/numa: documentation for per-cgroup numa, statistics 王贇
2019-12-10  2:19         ` [PATCH v5 0/2] sched/numa: introduce numa locality 王贇
2019-12-13  1:43         ` [PATCH v6 " 王贇
2019-12-13  1:47           ` [PATCH v6 1/2] sched/numa: introduce per-cgroup NUMA locality info 王贇
2020-01-03 15:14             ` Michal Koutný
2020-01-04  4:51               ` 王贇
2019-12-13  1:48           ` [PATCH v6 2/2] sched/numa: documentation for per-cgroup numa 王贇
2019-12-27  2:22           ` [PATCH v6 0/2] sched/numa: introduce numa locality 王贇
2020-01-17  2:19           ` 王贇
2020-01-19  6:08           ` [PATCH v7 " 王贇
2020-01-19  6:09             ` [PATCH v7 1/2] sched/numa: introduce per-cgroup NUMA locality info 王贇
2020-01-19  6:09             ` [PATCH v7 2/2] sched/numa: documentation for per-cgroup numa, statistics 王贇
2020-01-21  0:12               ` Randy Dunlap
2020-01-21  1:58                 ` 王贇
2020-01-21  1:56             ` [PATCH v8 0/2] sched/numa: introduce numa locality 王贇
2020-01-21  1:57               ` [PATCH v8 1/2] sched/numa: introduce per-cgroup NUMA locality info 王贇
2020-01-21  1:57               ` [PATCH v8 2/2] sched/numa: documentation for per-cgroup numa, statistics 王贇
2020-01-21  2:08                 ` Randy Dunlap

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191113080912.041918ce@lwn.net \
    --to=corbet@lwn.net \
    --cc=bsegall@google.com \
    --cc=dietmar.eggemann@arm.com \
    --cc=juri.lelli@redhat.com \
    --cc=keescook@chromium.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mcgrof@kernel.org \
    --cc=mgorman@suse.de \
    --cc=mingo@redhat.com \
    --cc=mkoutny@suse.com \
    --cc=paulmck@linux.ibm.com \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=vincent.guittot@linaro.org \
    --cc=yun.wang@linux.alibaba.com \
    --cc=yzaikin@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Fsdevel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \
		linux-fsdevel@vger.kernel.org
	public-inbox-index linux-fsdevel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git