Messages in this thread |  | | Subject | tbench regression in 2.6.25-rc1 | From | "Zhang, Yanmin" <> | Date | Fri, 15 Feb 2008 09:52:01 +0800 |
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Comparing with kernel 2.6.24, tbench result has regression with 2.6.25-rc1.
1) On 2 quad-core processor stoakley: 4%. 2) On 4 quad-core processor tigerton: more than 30%.
bisect located below patch.
b4ce92775c2e7ff9cf79cca4e0a19c8c5fd6287b is first bad commit commit b4ce92775c2e7ff9cf79cca4e0a19c8c5fd6287b Author: Herbert Xu <herbert@gondor.apana.org.au> Date: Tue Nov 13 21:33:32 2007 -0800
[IPV6]: Move nfheader_len into rt6_info
The dst member nfheader_len is only used by IPv6. It's also currently creating a rather ugly alignment hole in struct dst. Therefore this patch moves it from there into struct rt6_info.
As tbench uses ipv4, so the patch's real impact on ipv4 is it deletes nfheader_len in dst_entry. It might change cache line alignment.
To verify my finding, I just added nfheader_len back to dst_entry in 2.6.25-rc1 and reran tbench on the 2 machines. Performance could be recovered completely.
I started cpu_number*2 tbench processes. On my 16-core tigerton: #./tbench_srv & #./tbench 32 127.0.0.1
-yanmin
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