[PATCH 14/54] perf trace: Support setting cgroups as targets

From: Arnaldo Carvalho de Melo
Date: Thu Mar 08 2018 - 14:51:29 EST

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From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

One can set a cgroup as a default cgroup to be used by all events or
set cgroups with the 'perf stat' and 'perf record' behaviour, i.e.
'-G A' will be the cgroup for events defined so far in the command line.

Here in my main machine, with a kvm instance running a rhel6 guinea pig
I have:

# ls -la /sys/fs/cgroup/perf_event/ | grep drw
drwxr-xr-x. 14 root root 360 Mar 6 12:04 ..
drwxr-xr-x. 3 root root 0 Mar 6 15:05 machine.slice
#

So I can go ahead and use that cgroup hierarchy, say lets see what
syscalls are being emitted by threads in that 'machine.slice' hierarchy
that are taking more than 100ms:

# perf trace --duration 100 -G machine.slice
0.188 (249.850 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
250.274 (249.743 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
500.224 (249.755 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
750.097 (249.934 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
1000.244 (249.780 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
1250.197 (249.796 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
1500.124 (249.859 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
1750.076 (172.900 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
902.570 (1021.116 ms): qemu-system-x8/23667 ppoll(ufds: 0x558151e03180, nfds: 74, tsp: 0x7ffc00cd0900, sigsetsize: 8) = 1
1923.825 (305.133 ms): qemu-system-x8/23667 ppoll(ufds: 0x558151e03180, nfds: 74, tsp: 0x7ffc00cd0900, sigsetsize: 8) = 1
2000.172 (229.002 ms): CPU 0/KVM/23744 ioctl(fd: 16<anon_inode:kvm-vcpu:0>, cmd: KVM_RUN) = 0
^C #

If we look inside that cgroup hierarchy we get:

# ls -la /sys/fs/cgroup/perf_event/machine.slice/ | grep drw
drwxr-xr-x. 3 root root 0 Mar 6 15:05 .
drwxr-xr-x. 2 root root 0 Mar 6 16:16 machine-qemu\x2d2\x2drhel6.sandy.scope
#

There is just one, but lets say there were more and we would want to see
5 seconds worth of syscall summary for the threads in that cgroup:

# perf trace --summary -G machine.slice/machine-qemu\\x2d2\\x2drhel6.sandy.scope/ -a sleep 5

Summary of events:

qemu-system-x86 (23667), 143858 events, 24.2%

syscall calls total min avg max stddev
(msec) (msec) (msec) (msec) (%)
--------------- -------- --------- --------- --------- --------- ------
ppoll 28492 4348.631 0.000 0.153 11.616 1.05%
futex 19661 140.801 0.001 0.007 2.993 3.20%
read 18440 68.084 0.001 0.004 1.653 4.33%
ioctl 5387 24.768 0.002 0.005 0.134 1.62%

CPU 0/KVM (23744), 449455 events, 75.8%

syscall calls total min avg max stddev
(msec) (msec) (msec) (msec) (%)
--------------- -------- --------- --------- --------- --------- ------
ioctl 148364 3401.812 0.000 0.023 11.801 1.15%
futex 36131 404.127 0.001 0.011 7.377 2.63%
writev 29452 339.688 0.003 0.012 1.740 1.36%
write 11315 45.992 0.001 0.004 0.105 1.10%

#

See the documentation about how to set more than one cgroup for
different events in the same command line.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Hendrik Brueckner <brueckner@xxxxxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Richter <tmricht@xxxxxxxxxxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: https://lkml.kernel.org/n/tip-t126jh4occqvu0xdqlcjygex@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/Documentation/perf-trace.txt | 25 +++++++++++++++++
tools/perf/builtin-trace.c | 50 +++++++++++++++++++++++++++++++++
2 files changed, 75 insertions(+)

diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt
index 33a88e984e66..5a7035c5c523 100644
--- a/tools/perf/Documentation/perf-trace.txt
+++ b/tools/perf/Documentation/perf-trace.txt
@@ -63,6 +63,31 @@ filter out the startup phase of the program, which is often very different.
--uid=::
Record events in threads owned by uid. Name or number.

+-G::
+--cgroup::
+ Record events in threads in a cgroup.
+
+ Look for cgroups to set at the /sys/fs/cgroup/perf_event directory, then
+ remove the /sys/fs/cgroup/perf_event/ part and try:
+
+ perf trace -G A -e sched:*switch
+
+ Will set all raw_syscalls:sys_{enter,exit}, pgfault, vfs_getname, etc
+ _and_ sched:sched_switch to the 'A' cgroup, while:
+
+ perf trace -e sched:*switch -G A
+
+ will only set the sched:sched_switch event to the 'A' cgroup, all the
+ other events (raw_syscalls:sys_{enter,exit}, etc are left "without"
+ a cgroup (on the root cgroup, sys wide, etc).
+
+ Multiple cgroups:
+
+ perf trace -G A -e sched:*switch -G B
+
+ the syscall ones go to the 'A' cgroup, the sched:sched_switch goes
+ to the 'B' cgroup.
+
--filter-pids=::
Filter out events for these pids and for 'trace' itself (comma separated list).

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 1a93debc1e8d..5b81060a8117 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -19,6 +19,7 @@
#include <traceevent/event-parse.h>
#include <api/fs/tracing_path.h>
#include "builtin.h"
+#include "util/cgroup.h"
#include "util/color.h"
#include "util/debug.h"
#include "util/env.h"
@@ -83,6 +84,7 @@ struct trace {
struct perf_evlist *evlist;
struct machine *host;
struct thread *current;
+ struct cgroup *cgroup;
u64 base_time;
FILE *output;
unsigned long nr_events;
@@ -2370,6 +2372,34 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
trace__sched_stat_runtime))
goto out_error_sched_stat_runtime;

+ /*
+ * If a global cgroup was set, apply it to all the events without an
+ * explicit cgroup. I.e.:
+ *
+ * trace -G A -e sched:*switch
+ *
+ * Will set all raw_syscalls:sys_{enter,exit}, pgfault, vfs_getname, etc
+ * _and_ sched:sched_switch to the 'A' cgroup, while:
+ *
+ * trace -e sched:*switch -G A
+ *
+ * will only set the sched:sched_switch event to the 'A' cgroup, all the
+ * other events (raw_syscalls:sys_{enter,exit}, etc are left "without"
+ * a cgroup (on the root cgroup, sys wide, etc).
+ *
+ * Multiple cgroups:
+ *
+ * trace -G A -e sched:*switch -G B
+ *
+ * the syscall ones go to the 'A' cgroup, the sched:sched_switch goes
+ * to the 'B' cgroup.
+ *
+ * evlist__set_default_cgroup() grabs a reference of the passed cgroup
+ * only for the evsels still without a cgroup, i.e. evsel->cgroup == NULL.
+ */
+ if (trace->cgroup)
+ evlist__set_default_cgroup(trace->evlist, trace->cgroup);
+
err = perf_evlist__create_maps(evlist, &trace->opts.target);
if (err < 0) {
fprintf(trace->output, "Problems parsing the target to trace, check your options!\n");
@@ -2540,6 +2570,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
trace__symbols__exit(trace);

perf_evlist__delete(evlist);
+ cgroup__put(trace->cgroup);
trace->evlist = NULL;
trace->live = false;
return err;
@@ -2979,6 +3010,18 @@ static int trace__parse_events_option(const struct option *opt, const char *str,
return err;
}

+static int trace__parse_cgroups(const struct option *opt, const char *str, int unset)
+{
+ struct trace *trace = opt->value;
+
+ if (!list_empty(&trace->evlist->entries))
+ return parse_cgroups(opt, str, unset);
+
+ trace->cgroup = evlist__findnew_cgroup(trace->evlist, str);
+
+ return 0;
+}
+
int cmd_trace(int argc, const char **argv)
{
const char *trace_usage[] = {
@@ -3069,6 +3112,8 @@ int cmd_trace(int argc, const char **argv)
"print the PERF_RECORD_SAMPLE PERF_SAMPLE_ info, for debugging"),
OPT_UINTEGER(0, "proc-map-timeout", &trace.opts.proc_map_timeout,
"per thread proc mmap processing timeout in ms"),
+ OPT_CALLBACK('G', "cgroup", &trace, "name", "monitor event in cgroup name only",
+ trace__parse_cgroups),
OPT_UINTEGER('D', "delay", &trace.opts.initial_delay,
"ms to wait before starting measurement after program "
"start"),
@@ -3095,6 +3140,11 @@ int cmd_trace(int argc, const char **argv)
argc = parse_options_subcommand(argc, argv, trace_options, trace_subcommands,
trace_usage, PARSE_OPT_STOP_AT_NON_OPTION);

+ if ((nr_cgroups || trace.cgroup) && !trace.opts.target.system_wide) {
+ usage_with_options_msg(trace_usage, trace_options,
+ "cgroup monitoring only available in system-wide mode");
+ }
+
err = bpf__setup_stdout(trace.evlist);
if (err) {
bpf__strerror_setup_stdout(trace.evlist, err, bf, sizeof(bf));
--
2.14.3

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