[Xen-devel] Dom0 crash with apache bench (ab)

[Christoffer Dall <cdall@xxxxxxxxxxxxxxx>]

Hi,

I've been doing some performance comparisons lately, and wanted to compare the performance overhead of using Xen with apache bench, but unfortunately the Dom0 kernel crashes when hitting it with ab from a remote machine. Most other workloads seem to be stable, however, I do see similar crashes if hitting Dom0 mysql with a mysql benchmark with a high level of parallelism.

I use a 10G Mellanox MX354A Dual port FDR CX3 adapter for networking on a Dell PowerEdge R320 system with a Xeon E5-2450 and 16 GB of RAM.

Interestingly, we had a similarly looking issue on arm64 recently, but that was fixed with an APM-soecific fix to the hypervisor, so I am guessing this is unrelated, see: http://lists.xenproject.org/archives/html/xen-devel/2015-03/msg02731.html and the fix: http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=50dcb3de603927db2fd87ba09e29c817415aaa44

I have tried with several Linux versions, v3.13, v3.18, v4.0-rc4, and v4.1, same issue. I have tried with Xen 4.5-0 release, and the Ubuntu packaged Xen 4.4 release, same issue.

Examples of crash:
http://pastebin.ubuntu.com/11953498/
http://pastebin.ubuntu.com/11953443/

Running DomU with a bridge and running ab against apache running in a DomU also causes the system to crash.

Note: The server also has an embedded 1G Broadcom NIC (although not suitable for testing due to it being 1G and on a control network), and using that for the test does not cause a system crash, so this points to some difficulties with the Mellanox device and Xen.

Any ideas or advice is greatly appreciated, thanks.

-Christoffer

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