Re: REGRESSION: Performance regressions from switching anon_vma->lockto mutex

[Andi Kleen]

>       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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