Messages in this thread | | | Subject | Re: [PATCH v6 2/7] perf/x86/intel: Record branch type | From | "Jin, Yao" <> | Date | Mon, 24 Apr 2017 08:47:14 +0800 |
| |
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; >> +} >> + >> /*
| |