Messages in this thread | | | Subject | Re: [PATCH v6 2/7] perf/x86/intel: Record branch type | From | "Jin, Yao" <> | Date | Mon, 8 May 2017 08:49:44 +0800 |
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On 4/24/2017 8:47 AM, 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? >> >>> + >>> + 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 >
Hi,
Is this explanation OK? Since for tools part, it's Acked-by: Jiri Olsa. I just want to know if the kernel part is OK either?
Thanks Jin Yao
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