git: cc94d1bd7414 - main - pmc: pmc frontend stall analysis based on IBS

The branch main has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=cc94d1bd7414b309a62a379a8e614e3a3f9cd6d9

commit cc94d1bd7414b309a62a379a8e614e3a3f9cd6d9
Author:     Ali Mashtizadeh <ali@mashtizadeh.com>
AuthorDate: 2026-07-28 17:46:48 +0000
Commit:     Warner Losh <imp@FreeBSD.org>
CommitDate: 2026-07-28 19:27:45 +0000

    pmc: pmc frontend stall analysis based on IBS
    
    The frontend command uses AMD IBS frontend events to analyze the major
    sources of frontend stalls.  It displays a table breakind down the major
    causes of front end stalls.  This is a simple demonstration of the tools
    as you can use the filtering tools to limit the analysis to a subset of
    the samples including filtering by fetch latencies.
    
    Sponsored by: Netflix
    Reviewed by:    adrian, imp
    Differential Revision:  https://reviews.freebsd.org/D57779
---
 usr.sbin/pmc/cmd_pmc_frontend.cc | 242 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 242 insertions(+)

diff --git a/usr.sbin/pmc/cmd_pmc_frontend.cc b/usr.sbin/pmc/cmd_pmc_frontend.cc
new file mode 100644
index 000000000000..18ffd607bf21
--- /dev/null
+++ b/usr.sbin/pmc/cmd_pmc_frontend.cc
@@ -0,0 +1,242 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2026, Netflix, Inc.
+ *
+ * This software was developed by Ali Mashtizadeh under the sponsorship from
+ * Netflix, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include <sys/param.h>
+#include <sys/cpuset.h>
+#include <sys/event.h>
+#include <sys/queue.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/sysctl.h>
+#include <sys/time.h>
+#include <sys/ttycom.h>
+#include <sys/user.h>
+#include <sys/wait.h>
+
+#include <assert.h>
+#include <curses.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <kvm.h>
+#include <libgen.h>
+#include <limits.h>
+#include <locale.h>
+#include <math.h>
+#include <pmc.h>
+#include <pmclog.h>
+#include <regex.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include <libpmcstat.h>
+#include "cmd_pmc.h"
+
+#include <iostream>
+#include <map>
+#include <set>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+#include <dev/hwpmc/hwpmc_ibs.h>
+#include "display.hh"
+#include "view.hh"
+
+struct frontend {
+	syminfo		func;
+	int64_t		ocmiss;
+	int64_t		l2miss;
+	int64_t		l3miss;
+	int64_t		l1tlbmiss;
+	int64_t		l2tlbmiss;
+	int64_t		latency;
+	int64_t		samples;
+};
+
+static int sortcol = 2;
+
+class frontend_view : public pmcview
+{
+public:
+	frontend_view() : pmcview(), samples() { }
+	~frontend_view() { }
+
+	virtual void
+	callchain(struct pmclog_ev_callchain &p,
+	    ibsfetchinfo &f, __unused uintfptr_t *cc, __unused int len)
+	{
+		int usermode = PMC_CALLCHAIN_CPUFLAGS_TO_USERMODE(p.pl_cpuflags);
+
+		/* Ignore zeros */
+		if (IBS_FETCH_CTL_TO_LAT(f.ctl) == 0)
+			return;
+
+		auto inst = samples.find(f.linaddr);
+		if (inst == samples.end()) {
+			syminfo sym = addrtosymbol(usermode ? p.pl_pid : 0, f.linaddr);
+			if (sym.name == "")
+				return;
+
+			samples[f.linaddr] = frontend();
+			inst = samples.find(f.linaddr);
+			inst->second.func = sym;
+		}
+
+		/*
+		 * Save fetch cache and TLB miss counts
+		 */
+		if (f.ctl & IBS_FETCH_CTL_OPCACHEMISS)
+			inst->second.ocmiss += 1;
+		if (f.ctl & IBS_FETCH_CTL_L2MISS)
+			inst->second.l2miss += 1;
+		if (f.ctl & IBS_FETCH_CTL_L3MISS)
+			inst->second.l3miss += 1;
+
+		if (f.ctl & IBS_FETCH_CTL_L1TLBMISS)
+			inst->second.l1tlbmiss += 1;
+		if (f.ctl & IBS_FETCH_CTL_L2TLBMISS)
+			inst->second.l2tlbmiss += 1;
+
+		inst->second.latency += IBS_FETCH_CTL_TO_LAT(f.ctl);
+		inst->second.samples += 1;
+	}
+
+	virtual void
+	print()
+	{
+		title("IBS Frontend Analysis");
+
+		// Print header
+		table t = table();
+		t.addcolumn("Image", true);
+		t.addcolumn("Function", true);
+		t.addcolumn("Latency");
+		t.addcolumn("Samples");
+		t.addcolumn("OC Miss");
+		t.addcolumn("L2 Miss");
+		t.addcolumn("L3 Miss");
+		t.addcolumn("L1 TLB Miss");
+		t.addcolumn("L2 TLB Miss");
+
+		for (auto &kv : samples) {
+			std::vector<field> r;
+
+			r.emplace_back(kv.second.func.binary);
+			r.emplace_back(kv.second.func.to_string());
+			r.emplace_back(kv.second.latency);
+			r.emplace_back(kv.second.samples);
+			r.emplace_back(kv.second.ocmiss, kv.second.samples, true);
+			r.emplace_back(kv.second.l2miss, kv.second.samples, true);
+			r.emplace_back(kv.second.l3miss, kv.second.samples, true);
+			r.emplace_back(kv.second.l1tlbmiss, kv.second.samples, true);
+			r.emplace_back(kv.second.l2tlbmiss, kv.second.samples, true);
+
+			t.addrow(r);
+		}
+
+		t.sort(sortcol);
+		t.print();
+	}
+protected:
+	std::unordered_map<uint64_t, frontend> samples;
+};
+
+
+static struct option longopts[] = {
+	PMCFILTER_LOPTS,
+	{ "sort",	required_argument,	NULL,	's' },
+	{ NULL,		0,			NULL,	0 }
+};
+
+static void
+usage(void)
+{
+	printf("Usage: pmc frontend [options] [pmclog]\n\n");
+	printf("Analyze frontend bottlenecks\n\n");
+	printf("Options:\n");
+	printf("\t-s,--sort         Sort by event\n\n");
+	PMCFILTER_PRINTOPTS();
+}
+
+int
+cmd_pmc_frontend(int argc, char **argv)
+{
+	pmcfilter filter = pmcfilter();
+	const char *logfile = "default.log";
+	int option, logfd;
+
+	while ((option = getopt_long(argc, argv, PMCFILTER_SOPTS, longopts, NULL)) != -1) {
+		switch (option) {
+		PMCFILTER_CASE(filter)
+		case 's':
+			sortcol = atoi(optarg);
+			break;
+		case '?':
+		default:
+			usage();
+			exit(EX_USAGE);
+		}
+	}
+	argc -= optind;
+	argv += optind;
+	if (argc != 0 && argc != 1) {
+		usage();
+		exit(EX_USAGE);
+	}
+	if (argc == 1)
+		logfile = argv[0];
+
+	setup_screen();
+
+	if ((logfd = open(logfile, O_RDONLY)) < 0) {
+		errx(EX_OSERR, "ERROR: Cannot open \"%s\" for reading: %s.", logfile,
+		    strerror(errno));
+	}
+
+	frontend_view v = frontend_view();
+	v.setfilter(filter);
+	v.process(logfd);
+	v.print();
+
+	close(logfd);
+
+	return (0);
+}