Date: Wed, 16 Jan 2008 11:43:08 +0900
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [RFC][PATCH 3/5] add /dev/mem_notify device
Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, Marcelo Tosatti <marcelo@kvack.org>,
       Daniel Spang <daniel.spang@gmail.com>, Rik van Riel <riel@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>
In-Reply-To: <20080115134209.7b3c2f7e@lxorguk.ukuu.org.uk>
References: <20080115202711.11A6.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080115134209.7b3c2f7e@lxorguk.ukuu.org.uk>
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Hi Alan

> > > It also appears there is no way to wait for memory shortages (processes
> > > that can free memory easily) only for memory to start appearing.
> > 
> > poll() with never timeout don't fill your requirement?
> > to be honest, maybe I don't understand your afraid yet. sorry.
> 
> My misunderstanding. There is in fact no way to wait for memory to become
> available. The poll() method you provide works nicely waiting for
> shortages and responding to them by freeing memory.
> 
> It would be interesting to add FASYNC support to this. Some users have
> asked for a signal when memory shortage occurs (as IBM AIX provides
> this). FASYNC support would allow a SIGIO to be delivered from this
> device when memory shortages occurred. Poll as you have implemented is of
> course the easier way for a program to monitor memory and a better
> interface.

OK.
I will challenge implement at mem_notify v5.


- kosaki


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