linux-kernel - Re: [PATCH v4 0/4] cgroup notifications API and memory thresholds

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Date:	Mon, 4 Jan 2010 05:45:16 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	containers@...ts.linux-foundation.org, linux-mm@...ck.org,
	Paul Menage <menage@...gle.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Dan Malek <dan@...eddedalley.com>,
	Vladislav Buzov <vbuzov@...eddedalley.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Alexander Shishkin <virtuoso@...nd.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/4] cgroup notifications API and memory thresholds

* Kirill A. Shutemov <kirill@...temov.name> [2009-12-27 20:37:57]:

> On Sun, Dec 27, 2009 at 2:47 PM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > * Kirill A. Shutemov <kirill@...temov.name> [2009-12-27 04:08:58]:
> >
> >> This patchset introduces eventfd-based API for notifications in cgroups and
> >> implements memory notifications on top of it.
> >>
> >> It uses statistics in memory controler to track memory usage.
> >>
> >> Output of time(1) on building kernel on tmpfs:
> >>
> >> Root cgroup before changes:
> >>       make -j2  506.37 user 60.93s system 193% cpu 4:52.77 total
> >> Non-root cgroup before changes:
> >>       make -j2  507.14 user 62.66s system 193% cpu 4:54.74 total
> >> Root cgroup after changes (0 thresholds):
> >>       make -j2  507.13 user 62.20s system 193% cpu 4:53.55 total
> >> Non-root cgroup after changes (0 thresholds):
> >>       make -j2  507.70 user 64.20s system 193% cpu 4:55.70 total
> >> Root cgroup after changes (1 thresholds, never crossed):
> >>       make -j2  506.97 user 62.20s system 193% cpu 4:53.90 total
> >> Non-root cgroup after changes (1 thresholds, never crossed):
> >>       make -j2  507.55 user 64.08s system 193% cpu 4:55.63 total
> >>
> >> Any comments?
> >
> > Thanks for adding the documentation, now on to more critical questions
> >
> > 1. Any reasons for not using cgroupstats?
> 
> Could you explain the idea? I don't see how cgroupstats applicable for
> the task.

cgroupstats allows you to notify task statistics or send
notifications, hence the applicability.

> 
> > 2. Is there a user space test application to test this code.
> 
> Attached. It's not very clean, but good enough for testing propose.
> Example of usage:
> 
> $ echo '/cgroups/memory.usage_in_bytes 1G' | ./cgroup_event_monitor
> 

Thanks, I'll test it right now.

> >  IIUC,
> > I need to write a program that uses eventfd(2) and then passes
> > the eventfd descriptor and thresold to cgroup.*event* file and
> > then the program will get notified when the threshold is reached?
> 
> You need to pass eventfd descriptor, descriptor of control file to be
> monitored (memory.usage_in_bytes or memory.memsw.usage_in_bytes) and
> threshold.
> 
> Do you want to rename cgroup.event_control to cgroup.event?

No, event_control seems like a good name ATM.


-- 
	Balbir
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