Re: [PATCHES/RFC 1/5] perf bench uprobe + BPF skel

[Arnaldo Carvalho de Melo]

Em Wed, Jul 19, 2023 at 03:41:54PM -0700, Ian Rogers escreveu:
> On Wed, Jul 19, 2023 at 1:49 PM Arnaldo Carvalho de Melo
> <acme@xxxxxxxxxx> wrote:
> >
> > Hi,
> >
> >         This adds a 'perf bench' to test the overhead of uprobes + BPF
> > programs, for now just a few simple tests, but I plan to make it
> > possible to specify the functions to attach the uprobe + BPF, other BPF
> > operations dealing with maps, etc.
> >
> >         This is how it looks like now:
> >
> >   [root@five ~]# perf bench uprobe all
> >   # Running uprobe/baseline benchmark...
> >   # Executed 1,000 usleep(1000) calls
> >        Total time: 1,053,963 usecs
> >
> >    1,053.963 usecs/op
> >
> >   # Running uprobe/empty benchmark...
> >   # Executed 1,000 usleep(1000) calls
> >        Total time: 1,056,293 usecs +2,330 to baseline
> >
> >    1,056.293 usecs/op 2.330 usecs/op to baseline
> >
> >   # Running uprobe/trace_printk benchmark...
> >   # Executed 1,000 usleep(1000) calls
> >        Total time: 1,056,977 usecs +3,014 to baseline +684 to previous
> >
> >    1,056.977 usecs/op 3.014 usecs/op to baseline 0.684 usecs/op to previous
> >
> >   [root@five ~]
> >
> > I put it here:
> >
> >   https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=perf-bench-uprobe
> >
> >   git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git perf-bench-uprobe
> >
> > Further ideas, problems?
> 
> No problems. Perhaps it would be interesting to measure the uprobe
> overhead compared to say the overhead attaching to the nanosleep
> syscall?

Can you rephrase your question?

The test is comparing the overhead attaching to the clock_nanosleep
syscall:

[root@five ~]# strace -c ~/bin/perf bench uprobe baseline
# Running 'uprobe/baseline' benchmark:
# Executed 1,000 usleep(1000) calls
     Total time: 1,077,139 usecs

 1,077.139 usecs/op
==7056==LeakSanitizer has encountered a fatal error.
==7056==HINT: For debugging, try setting environment variable LSAN_OPTIONS=verbosity=1:log_threads=1
==7056==HINT: LeakSanitizer does not work under ptrace (strace, gdb, etc)
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ------------------
 52.87    0.002973           2      1000           clock_nanosleep
 22.55    0.001268           3       370           mmap
  8.87    0.000499           4       106           read
  5.42    0.000305           4        62           munmap
  2.42    0.000136           3        38           openat
  1.69    0.000095           1        48           mprotect
  1.28    0.000072           1        57           close
  1.19    0.000067           3        18           open
  0.98    0.000055           1        40         1 newfstatat
  0.44    0.000025           0        30           pread64
  0.44    0.000025           6         4           getdents64
  0.32    0.000018          18         1           readlink
  0.28    0.000016           2         8           write
  0.23    0.000013           1         9         4 prctl
  0.21    0.000012           6         2         2 access
  0.12    0.000007           0         8           madvise
  0.11    0.000006           1         4           clock_gettime
  0.11    0.000006           1         4           prlimit64
  0.07    0.000004           1         3           rt_sigaction
  0.07    0.000004           1         4           sigaltstack
  0.07    0.000004           4         1           sched_getaffinity
  0.05    0.000003           0         6           getpid
  0.04    0.000002           0         3           rt_sigprocmask
  0.04    0.000002           1         2         1 arch_prctl
  0.04    0.000002           1         2           futex
  0.04    0.000002           2         1           set_robust_list
  0.02    0.000001           1         1           set_tid_address
  0.02    0.000001           1         1           rseq
  0.00    0.000000           0         1           brk
  0.00    0.000000           0        14           sched_yield
  0.00    0.000000           0         1           clone
  0.00    0.000000           0         1           execve
  0.00    0.000000           0         1           wait4
  0.00    0.000000           0         1           gettid
------ ----------- ----------- --------- --------- ------------------
100.00    0.005623           3      1852         8 total
[root@five ~]#