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Re: [Xen-devel] Xen & I/O in clusters - Single Vs. Dual CPU issue

To: Xen Virtual Machine Monitor <xen-devel@xxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Xen & I/O in clusters - Single Vs. Dual CPU issue
From: Rune Johan Andresen <runejoha@xxxxxxxxxxx>
Date: Fri, 29 Oct 2004 19:05:47 +0200
Cc: Håvard Bjerke <Havard.Bjerke@xxxxxxxxxxx>
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Hi, we have validated the single CPU results in another single CPU cluster, and we still get an performance loss about 30%
(ca. 85 000 KB/s between two dom0 nodes (and NOT 114 000 KB/s),
Specs:
Ethernet controller: Intel Corp. 82547GI Gigabit Ethernet Controller
CPU: Intel(R) Pentium(R) 4 CPU 3.40GHz single CPU
RAM: 1 GB)

But, in a dual CPU cluster, Intel Xenon CPU 2.40 GHz Ethernet controller: Intel Corp. 82547GI Gigabit Ethernet Controller, we get only 1%
(from 114 000 KB/s -> 110 000 KB/s) performance loss.)

Both the single CPU clusters and the dual cluster are Xen 2.0 beta (2.4.26 kernel) with Red Hat Ent. 3

It seems to me that there is an issue with Xen and Gigabit ethernet controllers, where Xen is optimized for a dual core(?). As mentioned before we have more interrupts with Xen dom0 on eth0 than Native Linux
(we use bvt, not atropos)

Are there any Xen developers/testers which have tested Xen 2.0 on a single CPU cluster and can confirm (or not) these results?

Cheers,
Rune



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