转:perf - graphs

http://www.brendangregg.com/perf.html#FlameGraphs

Generation

The example flame graph was generated using perf_events and the FlameGraph tools:

# git clone https://github.com/brendangregg/FlameGraph  # or download it from github
# cd FlameGraph
# perf record -F 99 -ag -- sleep 60
# perf script | ./stackcollapse-perf.pl > out.perf-folded
# cat out.perf-folded | ./flamegraph.pl > perf-kernel.svg

The first perf command profiles CPU stacks, as explained earlier. I adjusted the rate to 99 Hertz here; I actually generated the flame graph from a 1000 Hertz profile, but I'd only use that if you had a reason to go faster, which costs more in overhead. The samples are saved in a perf.data file, which can be viewed using perf report:

# perf report --stdio
[...]
# Overhead          Command          Shared Object                               Symbol
# ........  ...............  .....................  ...................................
#
    72.18%            iperf  [kernel.kallsyms]      [k] iowrite16
                      |
                      --- iowrite16
                         |          
                         |--99.53%-- vp_notify
                         |          virtqueue_kick
                         |          start_xmit
                         |          dev_hard_start_xmit
                         |          sch_direct_xmit
                         |          dev_queue_xmit
                         |          ip_finish_output
                         |          ip_output
                         |          ip_local_out
                         |          ip_queue_xmit
                         |          tcp_transmit_skb
                         |          tcp_write_xmit
                         |          |          
                         |          |--98.16%-- tcp_push_one
                         |          |          tcp_sendmsg
                         |          |          inet_sendmsg
                         |          |          sock_aio_write
                         |          |          do_sync_write
                         |          |          vfs_write
                         |          |          sys_write
                         |          |          system_call
                         |          |          0x369e40e5cd
                         |          |          
                         |           --1.84%-- __tcp_push_pending_frames
[...]