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Re: [Xen-devel] Opteron server and NUMA

  • To: Alexander Charbonnet <alexander@xxxxxxxxxxxxxx>
  • From: Nicholas Lee <emptysands@xxxxxxxxx>
  • Date: Sun, 9 Oct 2005 00:16:51 +1300
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Sat, 08 Oct 2005 11:14:18 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

On 10/8/05, Alexander Charbonnet <alexander@xxxxxxxxxxxxxx> wrote:
> I now think that lack of NUMA support isn't the problem.  I've done some
> benchmarking of my database-backed Perl Web app with the Apache benchmark
> tool, "ab".  I ran the same query with differing total requests and
> concurrency.  After the first time, which I did manually before the tests,
> all the results will be in the database query cache.  Therefore, I don't
> expect any disk I/O.

Could be Net IO.  One thing I note with my Xen 2.0 setup is that it
wasn't very high performance.

There are a couple of emails I've noted but haven't had the time to try out yet:


"virtual eth devices had packet queueing disabled (txqueuelen:0 on
ifconfig), and had a 4k size max. ring buffer for
transfering packets between domains. Whenever that buffer would run
full, packets are dropped..."


"The problem is that the data structure in which the ring buffer is
organized has to fit into one memory page (4096 bytes)"


"default qdisc being inadequate"
"tc qdisc add dev eth0 root tbf rate 50mbit latency 20ms burst 50k"

One of the  problems with Xen at the moment is the lack of
documentation/cluebooks for stuff like this at the moment. Best
practice guides etc.  Still a learning process.

Nicholas Lee
gpg 8072 4F86 EDCD 4FC1 18EF  5BDD 07B0 9597 6D58 D70C

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