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

Andi Kleen
2011-06-15T20:57:31Z

> 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