lkml.org 
[lkml]   [2020]   [Jun]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH V2 08/23] perf/x86: Expose CPUID enumeration bits for arch LBR
From
Date


On 6/30/2020 11:01 AM, Peter Zijlstra wrote:
> On Fri, Jun 26, 2020 at 11:20:05AM -0700, kan.liang@linux.intel.com wrote:
>> From: Kan Liang <kan.liang@linux.intel.com>
>>
>> The LBR capabilities of Architecture LBR are retrieved from the CPUID
>> enumeration once at boot time. The capabilities have to be saved for
>> future usage.
>>
>> Several new fields are added into structure x86_pmu to indicate the
>> capabilities. The fields will be used in the following patches.
>>
>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
>> ---
>> arch/x86/events/perf_event.h | 5 +++++
>> arch/x86/include/asm/perf_event.h | 40 +++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 45 insertions(+)
>>
>> diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
>> index d04818b..9b0e533 100644
>> --- a/arch/x86/events/perf_event.h
>> +++ b/arch/x86/events/perf_event.h
>> @@ -690,6 +690,11 @@ struct x86_pmu {
>> const int *lbr_sel_map; /* lbr_select mappings */
>> bool lbr_double_abort; /* duplicated lbr aborts */
>> bool lbr_pt_coexist; /* (LBR|BTS) may coexist with PT */
>> + bool arch_lbr; /* Arch LBR supported */
>> +
>> + union cpuid28_eax lbr_eax;
>> + union cpuid28_ebx lbr_ebx;
>> + union cpuid28_ecx lbr_ecx;
>
> Why keep the full CPUID leaf here? What's wrong with something like:
>
> unsigned int lbr_depth_mask:8;
> unsigned int lbr_deep_c_reset:1;
> unsigned int lbr_lip:1;
> unsigned int lbr_cpl:1;
> unsigned int lbr_filter:1;
> unsigned int lbr_call_stack:1;
> unsigned int lbr_mispred:1;
> unsigned int lbr_timed_lbr:1;
> unsigned int lbr_br_type:1;
>
> That's only 2 bytes, instead of 24.

Yes, it can save the space.
I will add some codes in patch 14 to initialize these items in
intel_pmu_arch_lbr_init().

Thanks,
Kan

>
>> void (*lbr_reset)(void);
>> void (*lbr_read)(struct cpu_hw_events *cpuc);

\
 
 \ /
  Last update: 2020-06-30 17:36    [W:0.096 / U:0.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site