Date: Tue, 2 Jul 2013 14:38:22 -0400
From: Luiz Capitulino <lcapitulino@redhat.com>
To: Anton Vorontsov <anton@enomsg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Minchan Kim <minchan@kernel.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, mhocko@suse.cz, kmpark@infradead.org,
        hyunhee.kim@samsung.com
Subject: Re: [PATCH v2] vmpressure: implement strict mode
Message-ID: <20130702143822.4af2ebe3@redhat.com>
In-Reply-To: <20130702172409.GA13695@teo>
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	<20130628170917.GA12610@teo>
	<20130628144507.37d28ed9@redhat.com>
	<20130628185547.GA14520@teo>
	<20130628154402.4035f2fa@redhat.com>
	<20130629005637.GA16068@teo>
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On Tue, 2 Jul 2013 10:24:09 -0700
Anton Vorontsov <anton@enomsg.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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