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SubjectRe: [PATCH] perf arm64: Fix read PMU cpu slots
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在 2023/7/24 下午1:06, Haixin Yu 写道:
> Commit f8ad6018ce3c ("perf pmu: Remove duplication around
> EVENT_SOURCE_DEVICE_PATH") uses sysfs__read_ull to read a full
> sysfs path, which will never success. Fix it by read file directly.
>
> Signed-off-by: Haixin Yu <yuhaixin.yhx@linux.alibaba.com>
> ---
> tools/perf/arch/arm64/util/pmu.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/arch/arm64/util/pmu.c b/tools/perf/arch/arm64/util/pmu.c
> index 561de0cb6b95..512a8f13c4de 100644
> --- a/tools/perf/arch/arm64/util/pmu.c
> +++ b/tools/perf/arch/arm64/util/pmu.c
> @@ -54,10 +54,11 @@ double perf_pmu__cpu_slots_per_cycle(void)
> perf_pmu__pathname_scnprintf(path, sizeof(path),
> pmu->name, "caps/slots");
> /*
> - * The value of slots is not greater than 32 bits, but sysfs__read_int
> - * can't read value with 0x prefix, so use sysfs__read_ull instead.
> + * The value of slots is not greater than 32 bits, but
> + * filename__read_int can't read value with 0x prefix,
> + * so use filename__read_ull instead.
> */
> - sysfs__read_ull(path, &slots);
> + filename__read_ull(path, &slots);
> }
>
> return slots ? (double)slots : NAN;

Yes, the function perf_pmu__pathname_scnprintf returns the complete slots file path "/sys/bus/xxxxx/caps/slots",
and sysfs__read_ull will add the prefix "/sys" to the path, so the final file path becomes "/sys/sys/bus/xxxx/caps/slots"
which does not exist, and the slots file cannot be successfully read, so sysfs__read_ull needs to be changed to the
filename__read_ull.

I tested it and it works well.

Tested-by: Jing Zhang <renyu.zj@linux.alibaba.com>

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