Re: [PATCH RFC] x86: avoid atomic operation in test_and_set_bit_lock if possible

Eric Dumazet
2011-03-24T20:51:41Z

Le jeudi 24 mars 2011 à 21:00 +0100, Ingo Molnar a écrit :

> One good way to see cache bounces is to run a misses/accesses ratio profile:
>
> perf top -e cache-misses -e cache-references --count-filter 10
>

Oh well , something must be broken...

"perf top" is working here, but if I use any "-e ...." argument, it
fails :

# perf top -e cache-misses

Error: sys_perf_event_open() syscall returned with 2 (No such file or directory).
/bin/dmesg may provide additional information.

Fatal: No CONFIG_PERF_EVENTS=y kernel support configured?

# grep PERF_EVENTS .config
CONFIG_HAVE_PERF_EVENTS=y
CONFIG_PERF_EVENTS=y
CONFIG_HAVE_PERF_EVENTS_NMI=y

Nothing in dmesg...

uname -a
Linux ed001 2.6.38-08165-g2712750-dirty #517 SMP Thu Mar 24 21:31:00 CET 2011 i686 i686 i386 GNU/Linux