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    Subjecttbench regression in 2.6.25-rc1
    Comparing with kernel 2.6.24, tbench result has regression with

    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 <>
    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


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