perf trace: Support setting cgroups as targets

Commit-ID:  9ea42ba4411ac502e83baa9c61bb037d0a7355a0
Gitweb:     https://git.kernel.org/tip/9ea42ba4411ac502e83baa9c61bb037d0a7355a0
Author:     Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Tue, 6 Mar 2018 16:30:51 -0300
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Wed, 7 Mar 2018 10:22:26 -0300

perf trace: Support setting cgroups as targets

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.

---
 tools/perf/Documentation/perf-trace.txt | 25 +++++++++++++++++
 tools/perf/builtin-trace.c              | 50 +++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)

index 33a88e984e66..5a7035c5c523 100644
@@ -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).