lkml.org 
[lkml]   [2017]   [Apr]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v6 2/7] perf/x86/intel: Record branch type
From
Date


On 4/23/2017 9:55 PM, Jiri Olsa wrote:
> On Thu, Apr 20, 2017 at 08:07:50PM +0800, Jin Yao wrote:
>
> SNIP
>
>>
>> +#define X86_BR_TYPE_MAP_MAX 16
>> +
>> +static int
>> +common_branch_type(int type)
>> +{
>> + int i, mask;
>> + const int branch_map[X86_BR_TYPE_MAP_MAX] = {
>> + PERF_BR_CALL, /* X86_BR_CALL */
>> + PERF_BR_RET, /* X86_BR_RET */
>> + PERF_BR_SYSCALL, /* X86_BR_SYSCALL */
>> + PERF_BR_SYSRET, /* X86_BR_SYSRET */
>> + PERF_BR_INT, /* X86_BR_INT */
>> + PERF_BR_IRET, /* X86_BR_IRET */
>> + PERF_BR_JCC, /* X86_BR_JCC */
>> + PERF_BR_JMP, /* X86_BR_JMP */
>> + PERF_BR_IRQ, /* X86_BR_IRQ */
>> + PERF_BR_IND_CALL, /* X86_BR_IND_CALL */
>> + PERF_BR_NONE, /* X86_BR_ABORT */
>> + PERF_BR_NONE, /* X86_BR_IN_TX */
>> + PERF_BR_NONE, /* X86_BR_NO_TX */
>> + PERF_BR_CALL, /* X86_BR_ZERO_CALL */
>> + PERF_BR_NONE, /* X86_BR_CALL_STACK */
>> + PERF_BR_IND_JMP, /* X86_BR_IND_JMP */
>> + };
>> +
>> + type >>= 2; /* skip X86_BR_USER and X86_BR_KERNEL */
>> + mask = ~(~0 << 1);
> is that a fancy way to get 1 into the mask? what do I miss?
>
>> +
>> + for (i = 0; i < X86_BR_TYPE_MAP_MAX; i++) {
>> + if (type & mask)
>> + return branch_map[i];
> I wonder some bit search would be faster in here, but maybe not big deal
>
> jirka

I just think the branch_map[] doesn't contain many entries (16 entries
here), so maybe checking 1 bit one time should be acceptable. I just
want to keep the code simple.

But if the number of entries is more (e.g. 64), maybe it'd better check
2 or 4 bits one time.

Thanks
Jin Yao

>
>> +
>> + type >>= 1;
>> + }
>> +
>> + return PERF_BR_NONE;
>> +}
>> +
>> /*

\
 
 \ /
  Last update: 2017-04-24 02:48    [W:0.085 / U:2.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site