Messages in this thread |  | | Subject | Re: [PATCH v6 2/7] perf/x86/intel: Record branch type | From | "Jin, Yao" <> | Date | Tue, 9 May 2017 19:57:11 +0800 |
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On 5/9/2017 4:26 PM, Jiri Olsa wrote: > On Mon, Apr 24, 2017 at 08:47:14AM +0800, Jin, Yao wrote: >> >> 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? > you did not comment on this one
Sorry, I misunderstood that this comment and the next comment had the same meaning.
In the previous version, I used the switch/case to convert from X86_BR to PERF_BR. I got a comment from community that it'd better use a lookup table for conversion.
Since each bit in type represents a X86_BR type so I use a mask (0x1) to filter the bit. Yes, it looks I can also directly set 0x1 to mask.
I write the code "mask = ~(~0 << 1)" according to my coding habits. If you think I should change the code to "mask = 0x1", that's OK :)
>>>> + >>>> + 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. > ook > > jirka Sorry, what's the meaning of ook? Does it mean "OK"?
Thanks Jin Yao
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