[HEADS-UP] Rawhide: /tmp is now on tmpfs

[Richard W.M. Jones]

On Fri, Jun 01, 2012 at 11:00:57PM +0400, Alexey I. Froloff wrote:
> On Fri, Jun 01, 2012 at 01:50:55PM -0500, Michael Cronenworth wrote:
> > Not a single person who has claimed a performance or semantic win for
> > this /tmp move has replied when asked for proof.
> $ time dd if=/dev/zero of=/tmp/file bs=1M count=10240        
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 4.95536 s, 2.2 GB/s
> dd if=/dev/zero of=/tmp/file bs=1M count=10240  0.00s user 3.44s system 69% cpu 4.956 total
> 
> No visual shanges in system behavior.

I assume that your /tmp is on tmpfs; on all of *my* computers this
command would fail because the tmpfs would be too limited to store a
10GB file.

> $ time dd if=/dev/zero of=/var/tmp/file bs=1M count=10240 
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 59.2188 s, 181 MB/s
> dd if=/dev/zero of=/var/tmp/file bs=1M count=10240  0.00s user 54.26s system 91% cpu 59.239 total
> 
> SSD disk.  System becomes unresponsive for a couple of tens of seconds.

No problem here.  The machine isn't being unresponsive.

> $ time dd if=/dev/zero of=$HOME/file bs=1M count=10240 
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 75.1548 s, 143 MB/s
> dd if=/dev/zero of=$HOME/file bs=1M count=10240  0.01s user 71.30s system 94% cpu 1:15.16 total
> 
> SATA disk.  System becomes less responsive for a couple of seconds.

I can't reproduce this.  System works fine for me.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v