Daniel Wagner 0fb1170ee6 bpf: BPF based latency tracing ... BPF offers another way to generate latency histograms. We attach kprobes at trace_preempt_off and trace_preempt_on and calculate the time it takes to from seeing the off/on transition. The first array is used to store the start time stamp. The key is the CPU id. The second array stores the log2(time diff). We need to use static allocation here (array and not hash tables). The kprobes hooking into trace_preempt_on|off should not calling any dynamic memory allocation or free path. We need to avoid recursivly getting called. Besides that, it reduces jitter in the measurement. CPU 0 latency : count distribution 1 -> 1 : 0 | | 2 -> 3 : 0 | | 4 -> 7 : 0 | | 8 -> 15 : 0 | | 16 -> 31 : 0 | | 32 -> 63 : 0 | | 64 -> 127 : 0 | | 128 -> 255 : 0 | | 256 -> 511 : 0 | | 512 -> 1023 : 0 | | 1024 -> 2047 : 0 | | 2048 -> 4095 : 166723 |*************************************** | 4096 -> 8191 : 19870 |*** | 8192 -> 16383 : 6324 | | 16384 -> 32767 : 1098 | | 32768 -> 65535 : 190 | | 65536 -> 131071 : 179 | | 131072 -> 262143 : 18 | | 262144 -> 524287 : 4 | | 524288 -> 1048575 : 1363 | | CPU 1 latency : count distribution 1 -> 1 : 0 | | 2 -> 3 : 0 | | 4 -> 7 : 0 | | 8 -> 15 : 0 | | 16 -> 31 : 0 | | 32 -> 63 : 0 | | 64 -> 127 : 0 | | 128 -> 255 : 0 | | 256 -> 511 : 0 | | 512 -> 1023 : 0 | | 1024 -> 2047 : 0 | | 2048 -> 4095 : 114042 |*************************************** | 4096 -> 8191 : 9587 |** | 8192 -> 16383 : 4140 | | 16384 -> 32767 : 673 | | 32768 -> 65535 : 179 | | 65536 -> 131071 : 29 | | 131072 -> 262143 : 4 | | 262144 -> 524287 : 1 | | 524288 -> 1048575 : 364 | | CPU 2 latency : count distribution 1 -> 1 : 0 | | 2 -> 3 : 0 | | 4 -> 7 : 0 | | 8 -> 15 : 0 | | 16 -> 31 : 0 | | 32 -> 63 : 0 | | 64 -> 127 : 0 | | 128 -> 255 : 0 | | 256 -> 511 : 0 | | 512 -> 1023 : 0 | | 1024 -> 2047 : 0 | | 2048 -> 4095 : 40147 |*************************************** | 4096 -> 8191 : 2300 |* | 8192 -> 16383 : 828 | | 16384 -> 32767 : 178 | | 32768 -> 65535 : 59 | | 65536 -> 131071 : 2 | | 131072 -> 262143 : 0 | | 262144 -> 524287 : 1 | | 524288 -> 1048575 : 174 | | CPU 3 latency : count distribution 1 -> 1 : 0 | | 2 -> 3 : 0 | | 4 -> 7 : 0 | | 8 -> 15 : 0 | | 16 -> 31 : 0 | | 32 -> 63 : 0 | | 64 -> 127 : 0 | | 128 -> 255 : 0 | | 256 -> 511 : 0 | | 512 -> 1023 : 0 | | 1024 -> 2047 : 0 | | 2048 -> 4095 : 29626 |*************************************** | 4096 -> 8191 : 2704 |** | 8192 -> 16383 : 1090 | | 16384 -> 32767 : 160 | | 32768 -> 65535 : 72 | | 65536 -> 131071 : 32 | | 131072 -> 262143 : 26 | | 262144 -> 524287 : 12 | | 524288 -> 1048575 : 298 | | All this is based on the trace3 examples written by Alexei Starovoitov <ast@plumgrid.com>. Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Ingo Molnar <mingo@kernel.org> Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Acked-by: Alexei Starovoitov <ast@plumgrid.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>		2015-06-23 06:09:58 -07:00
..
bpf_helpers.h	bpf: introduce current->pid, tgid, uid, gid, comm accessors	2015-06-15 15:53:50 -07:00
bpf_load.c	samples/bpf: bpf_tail_call example for tracing	2015-05-21 17:07:59 -04:00
bpf_load.h
lathist_kern.c	bpf: BPF based latency tracing	2015-06-23 06:09:58 -07:00
lathist_user.c	bpf: BPF based latency tracing	2015-06-23 06:09:58 -07:00
libbpf.c
libbpf.h
Makefile	bpf: BPF based latency tracing	2015-06-23 06:09:58 -07:00
sock_example.c
sockex1_kern.c
sockex1_user.c
sockex2_kern.c
sockex2_user.c
sockex3_kern.c	bpf: allow programs to write to certain skb fields	2015-06-07 02:01:33 -07:00
sockex3_user.c	samples/bpf: bpf_tail_call example for networking	2015-05-21 17:07:59 -04:00
tcbpf1_kern.c	bpf: make programs see skb->data == L2 for ingress and egress	2015-06-07 02:01:33 -07:00
test_maps.c
test_verifier.c	bpf: allow programs to write to certain skb fields	2015-06-07 02:01:33 -07:00
tracex1_kern.c
tracex1_user.c
tracex2_kern.c	bpf: introduce current->pid, tgid, uid, gid, comm accessors	2015-06-15 15:53:50 -07:00
tracex2_user.c	bpf: introduce current->pid, tgid, uid, gid, comm accessors	2015-06-15 15:53:50 -07:00
tracex3_kern.c
tracex3_user.c
tracex4_kern.c
tracex4_user.c
tracex5_kern.c	samples/bpf: bpf_tail_call example for tracing	2015-05-21 17:07:59 -04:00
tracex5_user.c	samples/bpf: bpf_tail_call example for tracing	2015-05-21 17:07:59 -04:00