linux-kernel - Re: [RFC] Parallelize IO for e2fsck

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Date:	Fri, 25 Jan 2008 17:55:12 -0700
From:	Zan Lynx <zlynx@....org>
To:	Andreas Dilger <adilger@....com>
Cc:	Theodore Tso <tytso@....EDU>, Adrian Bunk <bunk@...nel.org>,
	Bodo Eggert <7eggert@....de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, Valdis.Kletnieks@...edu,
	David Chinner <dgc@....com>,
	Valerie Henson <val@...consulting.com>,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org, Ric Wheeler <ric@....com>
Subject: Re: [RFC] Parallelize IO for e2fsck


On Fri, 2008-01-25 at 04:09 -0700, Andreas Dilger wrote:
> On Jan 24, 2008  17:25 -0700, Zan Lynx wrote:
> > Have y'all been following the /dev/mem_notify patches?
> > http://article.gmane.org/gmane.linux.kernel/628653
> 
> Having the notification be via poll() is a very restrictive processing
> model.  Having the notification be via a signal means that any kind of
> process (and not just those that are event loop driven) can register
> a callback at some arbitrary point in the code and be notified.  I
> don't object to the poll() interface, but it would be good to have a
> signal mechanism also.

The commentary on the mem_notify threads claimed that the signal is
easily provided by setting up the file handle for SIGIO.

Yeah.  Here it is...copied from email written by KOSAKI Motohiro:

implement FASYNC capability to /dev/mem_notify.

<usage example>
        fd = open("/dev/mem_notify", O_RDONLY);

        fcntl(fd, F_SETOWN, getpid());

        flags = fcntl(fd, F_GETFL);
        fcntl(fd, F_SETFL, flags|FASYNC);  /* when low memory, receive SIGIO */
</usage example>
-- 
Zan Lynx <zlynx@....org>

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