linux-kernel - Re: [PATCH] vmpressure: implement strict mode

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Message-ID: <20130702175519.16148e5c@redhat.com>
Date:	Tue, 2 Jul 2013 17:55:19 -0400
From:	Luiz Capitulino <lcapitulino@...hat.com>
To:	Pavel Machek <pavel@....cz>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org, mhocko@...e.cz,
	minchan@...nel.org, anton@...msg.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] vmpressure: implement strict mode

On Tue, 2 Jul 2013 21:47:03 +0200
Pavel Machek <pavel@....cz> wrote:

> On Tue 2013-07-02 11:06:28, Luiz Capitulino wrote:
> > On Mon, 1 Jul 2013 10:51:03 +0200
> > Pavel Machek <pavel@....cz> wrote:
> > 
> > > Hi!
> > > 
> > > > diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
> > > > index ddf4f93..3c589cf 100644
> > > > --- a/Documentation/cgroups/memory.txt
> > > > +++ b/Documentation/cgroups/memory.txt
> > > > @@ -807,12 +807,14 @@ register a notification, an application must:
> > > >  
> > > >  - create an eventfd using eventfd(2);
> > > >  - open memory.pressure_level;
> > > > -- write string like "<event_fd> <fd of memory.pressure_level> <level>"
> > > > +- write string like "<event_fd> <fd of memory.pressure_level> <level> [strict]"
> > > >    to cgroup.event_control.
> > > >  
> > > 
> > > This is.. pretty strange interface. Would it be cleaner to do ioctl()?
> > > New syscall?
> > 
> > Are you referring to my new mode or to the whole thing?
> 
> Well. The interface was already very strange and you made it even
> worse.

The existing interface is the cgroup's notification mechanism, I think
discussing it is a bit out of scope for my extension.

Now, regarding my extension itself and the current vmpressure API, I
believe that delivering all events to user-space (ie. w/o any filtering
in the kernel) is a better solution.

Point is whether we can do it with the current vmpressure API (which
is cgroup based) or whether we should move to something else.
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