Re: [BUG] fatal hang untarring 90GB file, possibly writeback related.

James Bottomley
2011-04-28T14:49:50Z

On Thu, 2011-04-28 at 08:29 -0400, Chris Mason wrote:
> Excerpts from Colin Ian King's message of 2011-04-28 07:36:30 -0400:
> > One more data point to add, I've been looking at an identical issue when
> > copying large amounts of data. I bisected this - and the lockups occur
> > with commit
> > 3e7d344970673c5334cf7b5bb27c8c0942b06126 - before that I don't see the
> > issue. With this commit, my file copy test locks up after ~8-10
> > iterations, before this commit I can copy > 100 times and don't see the
> > lockup.
>
> Well, that's really interesting. I tried with compaction on here and
> couldn't trigger it, but this (very very lightly) tested patch might
> help.
>
> It moves the writeout throttle before the goto restart, and also makes
> sure we do at least one cond_resched before we loop.

It seems to take longer, but with a PREEMPT kernel, kswapd eventually
shoots up to 99% during the tar.

James