linux-kernel - Re: Unneeded kernel threads (xfs, jfs, gfs2)

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Message-ID: <20080513090311.GZ155679365@sgi.com>
Date:	Tue, 13 May 2008 19:03:11 +1000
From:	David Chinner <dgc@....com>
To:	Georgi Chorbadzhiyski <gf@...xsol.org>
Cc:	Donald Douwsma <donaldd@....com>, xfs@....sgi.com,
	jfs-discussion@...ts.sourceforge.net, cluster-devel@...hat.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Unneeded kernel threads (xfs, jfs, gfs2)

On Tue, May 13, 2008 at 11:30:59AM +0300, Georgi Chorbadzhiyski wrote:
> >>http://mirrors.unixsol.org/slackware/slackware-12.1/kernels/hugesmp.s/config 
> >
> >Your distro is building all of these modules into the kernel.
> >    CONFIG_XFS_FS=y
> >    CONFIG_JFS_FS=y
> >    CONFIG_GFS2_FS=y
> >
> >This isnt exactly standard practice, normally they'd be set to =m and only
> >used if required to mount a filesystem. You may want to ask the slackware
> >people why they chose to do this for their hugexxx.s kernels.
> 
> I know that they are compiled in the kernel, but since they
> are not used isn't starting their own kthreads kind of
> unnecessary? Surely the threads can be started on demand
> only when xfs/etc volume is mounted.

Sure - XFS will start another three kernel threads per filesystem
that gets mounted. And for good measure, it cleans them up again
on unmount. :)

The other threads are per-cpu workqueue threads that are shared
across all XFS filesystems in the system and hence are started
when XFS is initialised rather than when a mount occurs.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group
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