linux-kernel - Re: [PATCH] x86/events/intel/ds: Enable large PEBS for PERF_SAMPLE

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Date:   Thu, 19 May 2022 10:26:40 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Like Xu <like.xu.linux@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Stephane Eranian <eranian@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/events/intel/ds: Enable large PEBS for
 PERF_SAMPLE_WEIGHT type



On 5/19/2022 6:45 AM, Like Xu wrote:
> From: Like Xu <likexu@...cent.com>
> 
> Large PEBS could be enabled for the generic PERF_SAMPLE_WEIGHT sample

I think all the information required by the PERF_SAMPLE_WEIGHT is 
available in the pebs record. It should be OK to enable it for the large 
PEBS.

Can you please use the PERF_SAMPLE_WEIGHT_TYPE instead? It includes the 
new weight extension.

Thanks,
Kan

> type until other non-compatible flags such as PERF_SAMPLE_DATA_PAGE_SIZE
> (due to lack of munmap tracking) finally stop it.
> 
> Add PERF_SAMPLE_WEIGHT to LARGE_PEBS_FLAGS to save PMIs overhead.
> 
> Tested it with:
> 
> $ perf mem record -c 1000 workload
> Before: Captured and wrote 0.126 MB perf.data (958 samples) [958 PMIs]
> After: Captured and wrote 0.313 MB perf.data (4859 samples) [3 PMIs]
> 
> Cc: Kan Liang <kan.liang@...ux.intel.com>
> Cc: Stephane Eranian <eranian@...gle.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Reported-by: Yongchao Duan <yongduan@...cent.com>
> Signed-off-by: Like Xu <likexu@...cent.com>
> ---
>   arch/x86/events/perf_event.h | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
> index 21a5482bcf84..1ed0970d67e6 100644
> --- a/arch/x86/events/perf_event.h
> +++ b/arch/x86/events/perf_event.h
> @@ -136,7 +136,8 @@ struct amd_nb {
>   	PERF_SAMPLE_DATA_SRC | PERF_SAMPLE_IDENTIFIER | \
>   	PERF_SAMPLE_TRANSACTION | PERF_SAMPLE_PHYS_ADDR | \
>   	PERF_SAMPLE_REGS_INTR | PERF_SAMPLE_REGS_USER | \
> -	PERF_SAMPLE_PERIOD | PERF_SAMPLE_CODE_PAGE_SIZE)
> +	PERF_SAMPLE_PERIOD | PERF_SAMPLE_CODE_PAGE_SIZE | \
> +	PERF_SAMPLE_WEIGHT)
>   
>   #define PEBS_GP_REGS			\
>   	((1ULL << PERF_REG_X86_AX)    | \