linux-kernel - [PATCH v8 40/52] perf jevents: Add context switch metrics for Intel

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Message-ID: <20251113032040.1994090-41-irogers@google.com>
Date: Wed, 12 Nov 2025 19:20:28 -0800
From: Ian Rogers <irogers@...gle.com>
To: Adrian Hunter <adrian.hunter@...el.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Benjamin Gray <bgray@...ux.ibm.com>, 
	Caleb Biggers <caleb.biggers@...el.com>, Edward Baker <edward.baker@...el.com>, 
	Ian Rogers <irogers@...gle.com>, Ingo Molnar <mingo@...hat.com>, 
	James Clark <james.clark@...aro.org>, Jing Zhang <renyu.zj@...ux.alibaba.com>, 
	Jiri Olsa <jolsa@...nel.org>, John Garry <john.g.garry@...cle.com>, Leo Yan <leo.yan@....com>, 
	Namhyung Kim <namhyung@...nel.org>, Perry Taylor <perry.taylor@...el.com>, 
	Peter Zijlstra <peterz@...radead.org>, Samantha Alt <samantha.alt@...el.com>, 
	Sandipan Das <sandipan.das@....com>, Thomas Falcon <thomas.falcon@...el.com>, 
	Weilin Wang <weilin.wang@...el.com>, Xu Yang <xu.yang_2@....com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Subject: [PATCH v8 40/52] perf jevents: Add context switch metrics for Intel

Metrics break down context switches for different kinds of
instruction.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/pmu-events/intel_metrics.py | 58 ++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/tools/perf/pmu-events/intel_metrics.py b/tools/perf/pmu-events/intel_metrics.py
index bc3c50285916..9cf4bd8ac769 100755
--- a/tools/perf/pmu-events/intel_metrics.py
+++ b/tools/perf/pmu-events/intel_metrics.py
@@ -263,6 +263,63 @@ def IntelBr():
                        description="breakdown of retired branch instructions")
 
 
+def IntelCtxSw() -> MetricGroup:
+    cs = Event("context\\-switches")
+    metrics = [
+        Metric("lpm_cs_rate", "Context switches per second",
+               d_ratio(cs, interval_sec), "ctxsw/s")
+    ]
+
+    ev = Event("instructions")
+    metrics.append(Metric("lpm_cs_instr", "Instructions per context switch",
+                          d_ratio(ev, cs), "instr/cs"))
+
+    ev = Event("cycles")
+    metrics.append(Metric("lpm_cs_cycles", "Cycles per context switch",
+                          d_ratio(ev, cs), "cycles/cs"))
+
+    try:
+        ev = Event("MEM_INST_RETIRED.ALL_LOADS", "MEM_UOPS_RETIRED.ALL_LOADS")
+        metrics.append(Metric("lpm_cs_loads", "Loads per context switch",
+                              d_ratio(ev, cs), "loads/cs"))
+    except:
+        pass
+
+    try:
+        ev = Event("MEM_INST_RETIRED.ALL_STORES",
+                   "MEM_UOPS_RETIRED.ALL_STORES")
+        metrics.append(Metric("lpm_cs_stores", "Stores per context switch",
+                              d_ratio(ev, cs), "stores/cs"))
+    except:
+        pass
+
+    try:
+        ev = Event("BR_INST_RETIRED.NEAR_TAKEN", "BR_INST_RETIRED.TAKEN_JCC")
+        metrics.append(Metric("lpm_cs_br_taken", "Branches taken per context switch",
+                              d_ratio(ev, cs), "br_taken/cs"))
+    except:
+        pass
+
+    try:
+        l2_misses = (Event("L2_RQSTS.DEMAND_DATA_RD_MISS") +
+                     Event("L2_RQSTS.RFO_MISS") +
+                     Event("L2_RQSTS.CODE_RD_MISS"))
+        try:
+            l2_misses += Event("L2_RQSTS.HWPF_MISS",
+                               "L2_RQSTS.L2_PF_MISS", "L2_RQSTS.PF_MISS")
+        except:
+            pass
+
+        metrics.append(Metric("lpm_cs_l2_misses", "L2 misses per context switch",
+                              d_ratio(l2_misses, cs), "l2_misses/cs"))
+    except:
+        pass
+
+    return MetricGroup("lpm_cs", metrics,
+                       description=("Number of context switches per second, instructions "
+                                    "retired & core cycles between context switches"))
+
+
 def IntelIlp() -> MetricGroup:
     tsc = Event("msr/tsc/")
     c0 = Event("msr/mperf/")
@@ -678,6 +735,7 @@ def main() -> None:
         Smi(),
         Tsx(),
         IntelBr(),
+        IntelCtxSw(),
         IntelIlp(),
         IntelL2(),
         IntelLdSt(),
-- 
2.51.2.1041.gc1ab5b90ca-goog