On Thu, Oct 22, 2020 at 5:54 PM Jin Yao <[email protected]> wrote:
>
> Ian reports an issue that the metric DRAM_BW_Use often remains 0.
>
> The metric expression for DRAM_BW_Use on CLX/SKX:
>
> "( 64 * ( uncore_imc@cas_count_read@ + uncore_imc@cas_count_write@ ) /
> 1000000000 ) / duration_time"
>
> The counts of uncore_imc/cas_count_read/ and uncore_imc/cas_count_write/
> are scaled up by 64, that is to turn a count of cache lines into bytes,
> the count is then divided by 1000000000 to give GB.
>
> However, the counts of uncore_imc/cas_count_read/ and
> uncore_imc/cas_count_write/ have been scaled yet.
>
> The scale values are from sysfs, such as
> /sys/devices/uncore_imc_0/events/cas_count_read.scale.
> It's 6.103515625e-5 (64 / 1024.0 / 1024.0).
>
> So if we use original metric expression, the result is not correct.
>
> But the difficulty is, for SKL client, the counts are not scaled.
>
> The metric expression for DRAM_BW_Use on SKL:
>
> "64 * ( arb@event\\=0x81\\,umask\\=0x1@ + arb@event\\=0x84\\,umask\\=0x1@ ) /
> 1000000 / duration_time / 1000"
>
> root@kbl-ppc:~# perf stat -M DRAM_BW_Use -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 190 arb/event=0x84,umask=0x1/ # 1.86 DRAM_BW_Use
> 29,093,178 arb/event=0x81,umask=0x1/
> 1,000,703,287 ns duration_time
>
> 1.000703287 seconds time elapsed
>
> The result is expected.
>
> So the easy way is just change the metric expression for CLX/SKX.
> This patch changes the metric expression to:
>
> "( ( ( uncore_imc@cas_count_read@ + uncore_imc@cas_count_write@ ) * 1048576 )
> / 1000000000 ) / duration_time"
>
> 1048576 = 1024 * 1024.
>
> Before (tested on CLX):
>
> root@lkp-csl-2sp5 ~# perf stat -M DRAM_BW_Use -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 765.35 MiB uncore_imc/cas_count_read/ # 0.00 DRAM_BW_Use
> 5.42 MiB uncore_imc/cas_count_write/
> 1001515088 ns duration_time
>
> 1.001515088 seconds time elapsed
>
> After:
>
> root@lkp-csl-2sp5 ~# perf stat -M DRAM_BW_Use -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 767.95 MiB uncore_imc/cas_count_read/ # 0.80 DRAM_BW_Use
Nit, using ScaleUnit would allow this to be 0.80GB/s.
> 5.02 MiB uncore_imc/cas_count_write/
> 1001900010 ns duration_time
>
> 1.001900010 seconds time elapsed
>
> Fixes: 038d3b53c284 ("perf vendor events intel: Update CascadelakeX events to
> v1.08")
> Fixes: b5ff7f2799a4 ("perf vendor events: Update SkylakeX events to v1.21")
> Signed-off-by: Jin Yao <[email protected]>
Acked-by: Ian Rogers <[email protected]>
Thanks,
Ian
> ---
> tools/perf/pmu-events/arch/x86/cascadelakex/clx-metrics.json | 2 +-
> tools/perf/pmu-events/arch/x86/skylakex/skx-metrics.json | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/pmu-events/arch/x86/cascadelakex/clx-metrics.json
> b/tools/perf/pmu-events/arch/x86/cascadelakex/clx-metrics.json
> index de3193552277..00f4fcffa815 100644
> --- a/tools/perf/pmu-events/arch/x86/cascadelakex/clx-metrics.json
> +++ b/tools/perf/pmu-events/arch/x86/cascadelakex/clx-metrics.json
> @@ -329,7 +329,7 @@
> },
> {
> "BriefDescription": "Average external Memory Bandwidth Use for reads
> and writes [GB / sec]",
> - "MetricExpr": "( 64 * ( uncore_imc@cas_count_read@ +
> uncore_imc@cas_count_write@ ) / 1000000000 ) / duration_time",
> + "MetricExpr": "( ( ( uncore_imc@cas_count_read@ +
> uncore_imc@cas_count_write@ ) * 1048576 ) / 1000000000 ) / duration_time",
> "MetricGroup": "Memory_BW;SoC",
> "MetricName": "DRAM_BW_Use"
> },
> diff --git a/tools/perf/pmu-events/arch/x86/skylakex/skx-metrics.json
> b/tools/perf/pmu-events/arch/x86/skylakex/skx-metrics.json
> index f31794d3b926..0dd8b13b5cfb 100644
> --- a/tools/perf/pmu-events/arch/x86/skylakex/skx-metrics.json
> +++ b/tools/perf/pmu-events/arch/x86/skylakex/skx-metrics.json
> @@ -323,7 +323,7 @@
> },
> {
> "BriefDescription": "Average external Memory Bandwidth Use for reads
> and writes [GB / sec]",
> - "MetricExpr": "( 64 * ( uncore_imc@cas_count_read@ +
> uncore_imc@cas_count_write@ ) / 1000000000 ) / duration_time",
> + "MetricExpr": "( ( ( uncore_imc@cas_count_read@ +
> uncore_imc@cas_count_write@ ) * 1048576 ) / 1000000000 ) / duration_time",
> "MetricGroup": "Memory_BW;SoC",
> "MetricName": "DRAM_BW_Use"
> },
> --
> 2.17.1
>
