On Wed, Aug 13, 2014 at 12:57 AM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: > this example has two probes in C that use two different maps. > > 1st probe is the similar to dropmon.c. It attaches to kfree_skb tracepoint and > count number of packet drops at different locations > > 2nd probe attaches to kprobe/sys_write and computes a histogram of different > write sizes > > Usage: > $ sudo ex2 > > Should see: > writing bpf-5 -> /sys/kernel/debug/tracing/events/skb/kfree_skb/filter > writing bpf-8 -> /sys/kernel/debug/tracing/events/kprobes/sys_write/filter > location 0xffffffff816efc67 count 1 > > location 0xffffffff815d8030 count 1 > location 0xffffffff816efc67 count 3 > > location 0xffffffff815d8030 count 4 > location 0xffffffff816efc67 count 9 > > syscall write() stats > byte_size : count distribution > 1 -> 1 : 3141 |**** | > 2 -> 3 : 2 | | > 4 -> 7 : 14 | | > 8 -> 15 : 3268 |***** | > 16 -> 31 : 732 | | > 32 -> 63 : 20042 |************************************* | > 64 -> 127 : 12154 |********************** | > 128 -> 255 : 2215 |*** | > 256 -> 511 : 9 | | > 512 -> 1023 : 0 | | > 1024 -> 2047 : 1 | | This is pretty awesome. Given that this is tracing two tracepoints at once, I'd like to see a similar example where time is stored on the first tracepoint, retrieved on the second for a delta calculation, then presented with a similar histogram as seen above. Brendan -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
