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Message-ID: <20250529123456.1801-5-ravi.bangoria@amd.com> Date: Thu, 29 May 2025 12:34:56 +0000 From: Ravi Bangoria <ravi.bangoria@....com> To: Peter Zijlstra <peterz@...radead.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org> CC: Ravi Bangoria <ravi.bangoria@....com>, Ingo Molnar <mingo@...hat.com>, Stephane Eranian <eranian@...gle.com>, Ian Rogers <irogers@...gle.com>, "Kan Liang" <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>, "Leo Yan" <leo.yan@....com>, Joe Mario <jmario@...hat.com>, <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>, "Santosh Shukla" <santosh.shukla@....com>, Ananth Narayan <ananth.narayan@....com>, Sandipan Das <sandipan.das@....com> Subject: [PATCH 4/4] perf doc amd: Update perf-amd-ibs man page o Document software filtering capabilities provided by IBS kernel driver. o After recent perf-mem hist updates [1], the perf-mem example command in the perf-amd-ibs man page renders output differently. Unfortunately, there is no way to get the same aggregated output now. So use alternate command that can aggregate and show data at the command level. [1]: https://lore.kernel.org/r/20250430205548.789750-1-namhyung@kernel.org Signed-off-by: Ravi Bangoria <ravi.bangoria@....com> --- tools/perf/Documentation/perf-amd-ibs.txt | 72 +++++++++++++++++------ 1 file changed, 54 insertions(+), 18 deletions(-) diff --git a/tools/perf/Documentation/perf-amd-ibs.txt b/tools/perf/Documentation/perf-amd-ibs.txt index 55f80beae037..a543a68e3c94 100644 --- a/tools/perf/Documentation/perf-amd-ibs.txt +++ b/tools/perf/Documentation/perf-amd-ibs.txt @@ -33,9 +33,6 @@ if IBS is supported by the hardware and kernel. IBS Op PMU supports two events: cycles and micro ops. IBS Fetch PMU supports one event: fetch ops. -IBS PMUs do not have user/kernel filtering capability and thus it requires -CAP_SYS_ADMIN or CAP_PERFMON privilege. - IBS VS. REGULAR CORE PMU ------------------------ @@ -160,6 +157,38 @@ System-wide profile, fetch ops event, sampling period: 100000, Random enable etc. +IBS SW FILTERING +---------------- + +IBS PMU driver provides few additional software filtering capabilities. When +supported, kernel exposes config format through the following files: + + /sys/bus/event_source/devices/ibs_fetch/format/swfilt + /sys/bus/event_source/devices/ibs_op/format/swfilt + +1. Privilege (user/kernel) filtering. IBS PMUs do not support privilege +filtering in hardware so IBS driver supports it as a software filter. + + ibs_op/swfilt=1/u --> Only usermode samples + ibs_op/swfilt=1/k --> Only kernelmode samples + ibs_fetch/swfilt=1/u --> Only usermode samples + ibs_fetch/swfilt=1/k --> Only kernelmode samples + + Privilege filtering is always available when "swfilt" is supported. + So, kernel does not expose any separate PMU capability for this. + +2. Load/Store sampling. IBS OP PMU do not support load/store filtering in +hardware, so IBS driver supports it as a software filter. + + ibs_op/swfilt=1,ldop=1/ --> Only load samples + ibs_op/swfilt=1,stop=1/ --> Only store samples + ibs_op/swfilt=1,ldop=1,stop=1/ --> Load OR store samples + + Kernel creates following PMU capability file when load/store software + filtering is supported: + + /sys/bus/event_source/devices/ibs_op/caps/swfilt_ldst + PERF MEM AND PERF C2C --------------------- @@ -173,21 +202,28 @@ Below is a simple example of the perf mem tool. A normal perf mem report output will provide detailed memory access profile. However, it can also be aggregated based on output fields. For example: - # perf mem report -F mem,sample,snoop - Samples: 3M of event 'ibs_op//', Event count (approx.): 23524876 - Memory access Samples Snoop - N/A 1903343 N/A - L1 hit 1056754 N/A - L2 hit 75231 N/A - L3 hit 9496 HitM - L3 hit 2270 N/A - RAM hit 8710 N/A - Remote node, same socket RAM hit 3241 N/A - Remote core, same node Any cache hit 1572 HitM - Remote core, same node Any cache hit 514 N/A - Remote node, same socket Any cache hit 1216 HitM - Remote node, same socket Any cache hit 350 N/A - Uncached hit 18 N/A + # perf mem report -s comm,mem -H --stdio + Overhead Samples Command / Memory access + ......................... .......................................... + 66.46% 471728 cc1 + 34.70% 1393 RAM hit + 10.42% 370 Remote node, same socket RAM hit + 6.73% 10239 L2 hit + 5.84% 293953 N/A + 3.26% 163803 L1 hit + 3.16% 1796 L3 hit + 1.29% 95 Remote core, same node Any cache hit + 1.06% 73 Remote node, same socket Any cache hit + 0.00% 6 Uncached hit + 9.45% 44994 sh + 2.60% 131 RAM hit + 2.21% 219 Remote core, same node Any cache hit + 1.89% 190 Remote node, same socket Any cache hit + 1.02% 52 Remote node, same socket RAM hit + 0.72% 785 L2 hit + 0.60% 30149 N/A + 0.27% 13340 L1 hit + ... Please refer to their man page for more detail. -- 2.43.0
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