On Fri, 17 Jul 2020 14:40:53 -0300 Arnaldo Carvalho de Melo <a...@kernel.org> wrote:
> Say you use: > > ^C[root@ssdandy ~]# cyclictest --smp -um -p95 > # /dev/cpu_dma_latency set to 0us > policy: fifo: loadavg: 0.05 0.03 0.06 2/409 29072 > > T: 0 (29065) P:95 I:1000 C: 518 Min: 2 Act: 2 Avg: 2 Max: > 6 > T: 1 (29066) P:95 I:1500 C: 343 Min: 2 Act: 2 Avg: 2 Max: > 5 > T: 2 (29067) P:95 I:2000 C: 256 Min: 2 Act: 2 Avg: 2 Max: > 7 > T: 3 (29068) P:95 I:2500 C: 203 Min: 2 Act: 2 Avg: 2 Max: > 5 > T: 4 (29069) P:95 I:3000 C: 168 Min: 2 Act: 2 Avg: 3 Max: > 6 > T: 5 (29070) P:95 I:3500 C: 143 Min: 2 Act: 2 Avg: 2 Max: > 6 > T: 6 (29071) P:95 I:4000 C: 124 Min: 2 Act: 2 Avg: 2 Max: > 7 > T: 7 (29072) P:95 I:4500 C: 110 Min: 2 Act: 2 Avg: 2 Max: > > Then we do: > > # pidof cyclictest > 29064 > # > > If we use: > > [root@ssdandy ~]# perf record --pid 29064 > ^C[ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.052 MB perf.data (866 samples) ] > > [root@ssdandy ~]# perf report --task > # pid tid ppid comm > 0 0 -1 |swapper > 29064 29064 -1 |cyclictest > 29064 29065 -1 |cyclictest > 29064 29066 -1 |cyclictest > 29064 29067 -1 |cyclictest > 29064 29068 -1 |cyclictest > 29064 29069 -1 |cyclictest > 29064 29070 -1 |cyclictest > 29064 29071 -1 |cyclictest > 29064 29072 -1 |cyclictest > [root@ssdandy ~]# "ftrace" is inside the kernel. But you could specify all those PIDs in the set_ftrace_pid and set_event_pid files, and they will be traced. If you want to trace the children of those PIDs, you would need to set the options function function-fork and event-fork respectively. And then any time a process with a pid in the set_ftrace_pid or set_event_pid file forks, its child will also be added to that file and it too will be traced. If the fork options are set, then when a task exits, its pid will be removed from the file. echo 1 > options/function-fork echo 1 > options/event-fork > > If we are interested only on the thread running on CPU3 we can do: > > [root@ssdandy ~]# perf report --task > # pid tid ppid comm > 0 0 -1 |swapper > 29064 29064 -1 |cyclictest > 29064 29068 -1 |cyclictest > [root@ssdandy ~]# > > The first 29064 is just to have info on who created 29068, i.e.: > > Its just the synthesized info for 29068 creator: > > [root@ssdandy ~]# perf report -D | grep -w 29064/29064 > 0 0x4690 [0x30]: PERF_RECORD_COMM: cyclictest:29064/29064 > 0 0x46c0 [0x70]: PERF_RECORD_MMAP2 29064/29064: [0x400000(0xa000) @ 0 fd:00 > 136246288 0]: r-xp /usr/bin/cyclictest > 0 0x4730 [0x80]: PERF_RECORD_MMAP2 29064/29064: [0x7f990f505000(0x15000) @ 0 > fd:00 201479398 0]: r-xp /usr/lib64/libgcc_s-4.8.5-20150702.so.1 > 0 0x47b0 [0x70]: PERF_RECORD_MMAP2 29064/29064: [0x7f990f71b000(0x1c3000) @ 0 > fd:00 201334455 0]: r-xp /usr/lib64/libc-2.17.so > 0 0x4820 [0x78]: PERF_RECORD_MMAP2 29064/29064: [0x7f990fae9000(0xa000) @ 0 > fd:00 204604380 0]: r-xp /usr/lib64/libnuma.so.1.0.0 > 0 0x4898 [0x78]: PERF_RECORD_MMAP2 29064/29064: [0x7f990fcf5000(0x17000) @ 0 > fd:00 201335636 0]: r-xp /usr/lib64/libpthread-2.17.so > 0 0x4910 [0x78]: PERF_RECORD_MMAP2 29064/29064: [0x7f990ff11000(0x7000) @ 0 > fd:00 201335640 0]: r-xp /usr/lib64/librt-2.17.so > 0 0x4988 [0x70]: PERF_RECORD_MMAP2 29064/29064: [0x7f9910119000(0x22000) @ 0 > fd:00 203595299 0]: r-xp /usr/lib64/ld-2.17.so > 0 0x49f8 [0x60]: PERF_RECORD_MMAP2 29064/29064: [0x7fff0b52d000(0x2000) @ 0 > 00:00 0 0]: r-xp [vdso] > 0 0x4a58 [0x68]: PERF_RECORD_MMAP2 29064/29064: [0xffffffffff600000(0x1000) @ > 0 00:00 0 0]: r-xp [vsyscall] > [root@ssdandy ~]# > > No PERF_RECORD_SAMPLEs. > > Those are only for: > > [root@ssdandy ~]# perf report -D | grep PERF_RECORD_SAMPLE | head -5 > 147224656598815 0x4ac0 [0x28]: PERF_RECORD_SAMPLE(IP, 0x4001): 29064/29068: > 0xffffffffa8e5b568 period: 1 addr: 0 > 147224656606270 0x4ae8 [0x28]: PERF_RECORD_SAMPLE(IP, 0x4001): 29064/29068: > 0xffffffffa8e5b568 period: 1 addr: 0 > 147224656611284 0x4b10 [0x28]: PERF_RECORD_SAMPLE(IP, 0x4001): 29064/29068: > 0xffffffffa8e5b568 period: 5 addr: 0 > 147224656616225 0x4b38 [0x28]: PERF_RECORD_SAMPLE(IP, 0x4001): 29064/29068: > 0xffffffffa8e5b568 period: 35 addr: 0 > 147224656621152 0x4b60 [0x28]: PERF_RECORD_SAMPLE(IP, 0x4001): 29064/29068: > 0xffffffffa8e5b568 period: 252 addr: 0 > [root@ssdandy ~]# > > [root@ssdandy ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d: -f3 | > sort -u > 29064/29068 The above can somewhat be done in trace-cmd, but not fully. But that's all userspace commands, nothing with the kernel. > [root@ssdandy ~]# > > Is there a way in ftrace to ask for a pid and its children? Pre-existing > and and new ones the --pid specified will create after we start > monitoring? > As described above, yes. :-) -- Steve
