From: "Richard W.M. Jones" <rjones@redhat.com>
Subject: Re: fstrim has no effect on a just-mounted filesystem
Date: Tue, 11 Mar 2014 23:07:15 +0000
Message-ID: <20140311230715.GA19648@redhat.com>
References: <20140311213932.GA19176@redhat.com>
 <531F8456.2020404@redhat.com>
 <20140311220013.GV1346@redhat.com>
 <531F8953.1030702@redhat.com>
 <20140311225932.GW1346@redhat.com>
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Cc: linux-ext4@vger.kernel.org
To: Eric Sandeen <sandeen@redhat.com>
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In-Reply-To: <20140311225932.GW1346@redhat.com>
Sender: linux-ext4-owner@vger.kernel.org

On Tue, Mar 11, 2014 at 10:59:32PM +0000, Richard W.M. Jones wrote:
> On Tue, Mar 11, 2014 at 05:08:19PM -0500, Eric Sandeen wrote:
> > blktrace is probably the place to start.  Do you see discard
> > requests?  then ext4 is doing its job.  If not, we can trace
> > ext4 to see why it's not issuing them, assuming there really
> > is work to do.
> 
> At the moment I can't get this to work.  The script I'm using is:
> 
> ----------------------------------------------------------------------
> set -e
> set -x
> trace-cmd record -e all -o /tmp/trace &
> pid=$!
> fstrim /sysroot
> kill $pid; sleep 2
> trace-cmd report -i /tmp/trace
> ----------------------------------------------------------------------

I got it to work by using:

----------------------------------------------------------------------
set -e
set -x
trace-cmd record -e all fstrim /sysroot
trace-cmd report
----------------------------------------------------------------------

The output is absolutely huge and I didn't capture it.

However just the act of doing the tracing *caused* the trim to happen
properly in the underlying disk.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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