linux-kernel - Re: [PATCH v2] vmpressure: implement strict mode

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Message-ID: <20130702143822.4af2ebe3@redhat.com>
Date:	Tue, 2 Jul 2013 14:38:22 -0400
From:	Luiz Capitulino <lcapitulino@...hat.com>
To:	Anton Vorontsov <anton@...msg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mhocko@...e.cz, kmpark@...radead.org,
	hyunhee.kim@...sung.com
Subject: Re: [PATCH v2] vmpressure: implement strict mode

On Tue, 2 Jul 2013 10:24:09 -0700
Anton Vorontsov <anton@...msg.org> wrote:

> > Honestly, what Andrew suggested is the best design for me: apps
> > are notified on all events but the event name is sent to the application.
> 
> I am fine with this approach (or any other, I'm really indifferent to the
> API itself -- read/netlink/notification per file/whatever for the
> payload),

That's a very good thing because we've managed to agree on something :)

I'm also indifferent to the API, as long as we have 100% of the policy
in user-space. To me this means we do absolutely no filtering in the
kernel, which in turn means user-space gets all the events. Of course,
we need the event name as a payload.

Do we agree this solves all use-cases we have discussed so far?

> except that you still have the similar problem:
> 
>   read() old    read() new
>   --------------------------
>        "low"           "low"
>        "low"           "foo" -- the app does not know what does this mean
>        "med"           "bar" -- ditto

It can just ignore it, have a special handling, log it, fail or whatever.
That's the good of having the policy in user-space.
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