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    SubjectRe: REGRESSION: Performance regressions from switching anon_vma->lock to mutex

    > 7.44% exim [kernel.kallsyms] [k] format_decode
    > |
    > --- format_decod


    This is a glibc issue. exim calls libdb and libdb asks sysconf for the
    number of CPUs to tune
    its locking, and glibc reads /proc/stat. And /proc/stat is incredible slow.

    I would blame glibc, but in this case it's really the kernel to blame
    for not providing proper
    interface.

    This was my motivation for the sysconf() syscall I submitted some time ago.
    https://lkml.org/lkml/2011/5/13/455

    Anyways a quick workaround is to use this LD_PRELOAD:
    http://halobates.de/smallsrc/sysconf.c
    But it's not 100% equivalent.

    -Andi





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