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From Keith W <keith.w...@gmail.com>
Subject Ubuntu4/5 (juno/janus) filesystem operations are slow in comparison with other Ubuntu1-3.
Date Mon, 12 Nov 2012 09:09:43 GMT
Hello Builds

I'm investigating a regular test failure we (Qpid) see on one of our
Jenkins jobs (Qpid-Java-Java-DBY-TestMatrix).  The job is a matrix
that is tied to the ubuntu label.   I notice that the test failure (a
timeout) seems to occur when ubuntu4 or 5 is chosen as a build slave.
Tests that normally take a seconds or less extend to tens of seconds
or worse and the job is caught by the build timeout plugin  and a
failure results.

I'm still investigating, but at the moment, the application logs are
pointing to a very slow filesystem as a likely cause.  I also see
similar results timing sync and dd commands from a jenkins job.
Script fragment and results are below.

It would be helpful to me to know the spec of juno and janus machines
including their filesystem spec and config (eg. RAID)   (the details
are absent from www.apache.org/dev/machines.html).   Are these true
machines or guest VMs?  Are you aware of anything else that may cause
slow filesystem performance?

Kind regards, Keith Wall.



Script:

time sync
sh -c 'dd if=/dev/zero of=ddfile bs=8k count=200000 && sync'
time sync

ubuntu5

time sync (before)
real	0m6.513s
user	0m0.000s
sys	0m0.584s
200000+0 records in
200000+0 records out
1638400000 bytes (1.6 GB) copied, 3.58202 s, 457 MB/s
real	0m32.567s
user	0m0.016s
sys	0m4.116s
time sync (after)
real	0m1.378s
user	0m0.000s
sys	0m0.552s

ubuntu3 (for comparison):

time sync (before)
real	0m0.491s
user	0m0.000s
sys	0m0.372s

1638400000 bytes (1.6 GB) copied, 1.25777 s, 1.3 GB/s
real	0m4.696s
user	0m0.012s
sys	0m1.608s

time sync (after)
real	0m0.376s
user	0m0.000s
sys	0m0.364s

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