Messages in this thread Patch in this message | | | From | Arnaldo Carvalho de Melo <> | Subject | [PATCH 06/11] perf bpf: Add kprobe example to catch 5s naps | Date | Wed, 16 May 2018 11:49:03 -0300 |
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From: Arnaldo Carvalho de Melo <acme@redhat.com>
Description:
. Disable strace like syscall tracing (--no-syscalls), or try tracing just some (-e *sleep).
. Attach a filter function to a kernel function, returning when it should be considered, i.e. appear on the output:
$ cat tools/perf/examples/bpf/5sec.c #include <bpf.h>
SEC("func=hrtimer_nanosleep rqtp->tv_sec") int func(void *ctx, int err, long sec) { return sec == 5; }
char _license[] SEC("license") = "GPL"; int _version SEC("version") = LINUX_VERSION_CODE; $
. Run it system wide, so that any sleep of >= 5 seconds and < than 6 seconds gets caught.
. Ask for callgraphs using DWARF info, so that userspace can be unwound
. While this is running, run something like "sleep 5s".
# perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c/call-graph=dwarf/ 0.000 perf_bpf_probe:func:(ffffffff9811b5f0) tv_sec=5 hrtimer_nanosleep ([kernel.kallsyms]) __x64_sys_nanosleep ([kernel.kallsyms]) do_syscall_64 ([kernel.kallsyms]) entry_SYSCALL_64 ([kernel.kallsyms]) __GI___nanosleep (/usr/lib64/libc-2.26.so) rpl_nanosleep (/usr/bin/sleep) xnanosleep (/usr/bin/sleep) main (/usr/bin/sleep) __libc_start_main (/usr/lib64/libc-2.26.so) _start (/usr/bin/sleep) ^C#
Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Wang Nan <wangnan0@huawei.com> Link: https://lkml.kernel.org/n/tip-2nmxth2l2h09f9gy85lyexcq@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> --- tools/perf/examples/bpf/5sec.c | 44 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 tools/perf/examples/bpf/5sec.c
diff --git a/tools/perf/examples/bpf/5sec.c b/tools/perf/examples/bpf/5sec.c new file mode 100644 index 000000000000..3d1ed34aec8b --- /dev/null +++ b/tools/perf/examples/bpf/5sec.c @@ -0,0 +1,44 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + Description: + + . Disable strace like syscall tracing (--no-syscalls), or try tracing + just some (-e *sleep). + + . Attach a filter function to a kernel function, returning when it should + be considered, i.e. appear on the output. + + . Run it system wide, so that any sleep of >= 5 seconds and < than 6 + seconds gets caught. + + . Ask for callgraphs using DWARF info, so that userspace can be unwound + + . While this is running, run something like "sleep 5s". + + # perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c/call-graph=dwarf/ + 0.000 perf_bpf_probe:func:(ffffffff9811b5f0) tv_sec=5 + hrtimer_nanosleep ([kernel.kallsyms]) + __x64_sys_nanosleep ([kernel.kallsyms]) + do_syscall_64 ([kernel.kallsyms]) + entry_SYSCALL_64 ([kernel.kallsyms]) + __GI___nanosleep (/usr/lib64/libc-2.26.so) + rpl_nanosleep (/usr/bin/sleep) + xnanosleep (/usr/bin/sleep) + main (/usr/bin/sleep) + __libc_start_main (/usr/lib64/libc-2.26.so) + _start (/usr/bin/sleep) + ^C# + + Copyright (C) 2018 Red Hat, Inc., Arnaldo Carvalho de Melo <acme@redhat.com> +*/ + +#include <bpf.h> + +SEC("func=hrtimer_nanosleep rqtp->tv_sec") +int func(void *ctx, int err, long sec) +{ + return sec == 5; +} + +char _license[] SEC("license") = "GPL"; +int _version SEC("version") = LINUX_VERSION_CODE; -- 2.14.3
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