perf_counter, x86: Extend perf_counter Pentium M support
I've attached a patch to remove the Pentium M special casing of
EMON and as noticed at least with my Pentium M the hardware PMU
now works:
Performance counter stats for '/bin/ls /var/tmp':
1.809988 task-clock-msecs # 0.125 CPUs
1 context-switches # 0.001 M/sec
0 CPU-migrations # 0.000 M/sec
224 page-faults # 0.124 M/sec
1425648 cycles # 787.656 M/sec
912755 instructions # 0.640 IPC
Vince suggested that this code was trying to address erratum
Y17 in Pentium-M's:
http://download.intel.com/support/processors/mobile/pm/sb/25266532.pdf
But that erratum (related to IA32_MISC_ENABLES.7) does not
affect perfcounters as we dont use this toggle to disable RDPMC
and WRMSR/RDMSR access to performance counters. We keep cr4's
bit 8 (X86_CR4_PCE) clear so unprivileged RDPMC access is not
allowed anyway.
Cc: Vince Weaver <vince@deater.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@googlemail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
1 file changed
