[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20160811164150.GB7296@nazgul.tnic>
Date: Thu, 11 Aug 2016 18:41:50 +0200
From: Borislav Petkov <bp@...en8.de>
To: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] perf/x86/amd: Make HW_CACHE_REFERENCES and
HW_CACHE_MISSES measure L2
Drop stable from CC.
On Thu, Aug 11, 2016 at 04:21:42PM +0100, Matt Fleming wrote:
> While the Intel PMU monitors the LLC when perf enables the
> HW_CACHE_REFERENCES and HW_CACHE_MISSES events, these events monitor
> L1 instruction cache fetches (0x0080) and instruction cache misses
> (0x0081) on the AMD PMU.
>
> This is extremely confusing when monitoring the same workload across
> Intel and AMD machines, since parameters like,
>
> $ perf stat -e cache-references,cache-misses
>
> measure completely different things.
>
> Instead, make the AMD PMU measure instruction/data cache fill requests
> to the L2 and instruction/data cache misses in the L2 when
> HW_CACHE_REFERENCES and HW_CACHE_MISSES are enabled, respectively.
> That way the events measure unified caches on both platforms.
I guess that's closer.
Even though LLC is not always L2 on AMD (some have L3). Btw,
what are the exact events for PERF_COUNT_HW_CACHE_REFERENCES and
PERF_COUNT_HW_CACHE_MISSES called on Intel?
I could try to find better/more fitting event selectors on AMD...
> Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: <stable@...r.kernel.org>
> ---
> arch/x86/events/amd/core.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
> index e07a22bb9308..8fd8bf79f32b 100644
> --- a/arch/x86/events/amd/core.c
> +++ b/arch/x86/events/amd/core.c
> @@ -119,8 +119,8 @@ static const u64 amd_perfmon_event_map[PERF_COUNT_HW_MAX] =
> {
> [PERF_COUNT_HW_CPU_CYCLES] = 0x0076,
> [PERF_COUNT_HW_INSTRUCTIONS] = 0x00c0,
> - [PERF_COUNT_HW_CACHE_REFERENCES] = 0x0080,
> - [PERF_COUNT_HW_CACHE_MISSES] = 0x0081,
> + [PERF_COUNT_HW_CACHE_REFERENCES] = 0x037d,
> + [PERF_COUNT_HW_CACHE_MISSES] = 0x037e,
> [PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = 0x00c2,
> [PERF_COUNT_HW_BRANCH_MISSES] = 0x00c3,
> [PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] = 0x00d0, /* "Decoder empty" event */
Btw, there's also amd_event_mapping in arch/x86/kvm/pmu_amd.c which has
duplicated amd_perfmon_event_map. Would need adjusting too.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
Powered by blists - more mailing lists