linux-kernel - Re: 3.6.0 ext4 dump/filemap

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Message-ID: <20121029223503.GA9532@thunk.org>
Date:	Mon, 29 Oct 2012 18:35:03 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Justin Piszcz <jpiszcz@...idpixels.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 3.6.0 ext4 dump/filemap_fault?

On Mon, Oct 29, 2012 at 05:51:37PM -0400, Justin Piszcz wrote:
> 
> > What happened afterwards?
> It did eventually complete.
> 
> > How much memory do you have in your system?
> 32GB memory/32GB swap
> > Did the system continue, and did the sync command (I presume you ran
> > "sync" from the command line?)  finally return to the command prompt?
> In this case I did not run sync, I waited for the processes/dump/etc
> to complete.

OK, well *some* process must have issued a sync system call, since
that was what triggered the soft lockup.  If half your memory was
dirtied, then the time it might take to write back 16 gigs would
roughly:

   (16 GB * 1024 MB/G) /  100 MB/s = 163 seconds

... which would be enough to trigger the soft lockup error.

    	  	   	     	     	      - Ted

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