[issue1556] many processes stuck in "hmrrcm", system unusable

[Steve O'Hara-Smith]

On Mon, 05 Oct 2009 00:53:46 +0200
"Simon 'corecode' Schubert" <corecode at fs.ei.tum.de> wrote:

> Steve O'Hara-Smith wrote:
> > 	If you are suffering the latter then I would certainly agree
> > with the suggestion to mount with noatime, I do this routinely for any
> > file system which gets heavy random file access because atime updates
> > will cripple performance on any filesystem I have ever used by making
> > the discs spend more time seeking than reading. It does sound like
> > hammer may suffer more than other filesystems from this.
> 
> This is possible.  However I don't want to mount all my file systems 
> noatime.  I'm using atime regularly for various purposes, so I don't 
> really want to run without it.  Maybe I can try it though.

	I certainly wouldn't mount all filesystems noatime, just ones that
take a lot of random access traffic.

> I think even with atime turned on, a filesystem needs to perform 
> acceptable.  I'm not talking about high throughput.  I'm talking about 
> xterm+shell taking >10s until the prompt appears, or vim occasionally 
> hanging for several seconds.

	That's something I have never seen happening, even when I do
have a high load of filesystem activity, discs running at 100% for extended
periods while largeish trees get moved around. The system certainly gets
sluggish under that kind of load but nowhere near as bad as that.

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