xen-devel
[Xen-devel] Re: Xen performance and Dbench
Todd Deshane wrote:
dbench is an interesting test since it is basically an I/O test (Samba test)
http://samba.org/ftp/tridge/dbench/README
dbench is actually *not* an I/O test. It mostly stresses a filesystems
interaction with the page cache. It's heavily threaded and tends to
scale okay but it's rarely impacted heavily by the underlying storage
systems I/O performance. It tends to demonstrate shadow page table SMP
scalability more than I/O performance.
The OLS paper referenced really had bad methodologies. If you read
carefully, their host system was a 2-way system. They ran all of the
guests UP though. Since they didn't do a parallel make, it wasn't very
obvious for their "kernel build" but it became obvious with dbench since
there were multiple threads.
So native and "VServer" had access to both CPU cores whereas Xen, KVM,
et al were only running on a single core. There's no way dbench is 30%
of native under Xen. That should have been a big red flag that
something was wrong.
Regards,
Anthony Liguori
I don't know if dbench is the best test to determine if Xen (or other
virts) need
to be fixed.
Cheers,
Todd
===================================
Thanks... for the memory
I really could use more / My throughput's on the floor
The balloon is flat / My swap disk's fat / I've OOM's in store
Overcommitted so much
(with apologies to the late great Bob Hope)
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