Linux Perf
5sec.c
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// SPDX-License-Identifier: GPL-2.0
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/*
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Description:
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. Disable strace like syscall tracing (--no-syscalls), or try tracing
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just some (-e *sleep).
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. Attach a filter function to a kernel function, returning when it should
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be considered, i.e. appear on the output.
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. Run it system wide, so that any sleep of >= 5 seconds and < than 6
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seconds gets caught.
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. Ask for callgraphs using DWARF info, so that userspace can be unwound
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. While this is running, run something like "sleep 5s".
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. If we decide to add tv_nsec as well, then it becomes:
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int probe(hrtimer_nanosleep, rqtp->tv_sec rqtp->tv_nsec)(void *ctx, int err, long sec, long nsec)
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I.e. add where it comes from (rqtp->tv_nsec) and where it will be
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accessible in the function body (nsec)
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# perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c/call-graph=dwarf/
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0.000 perf_bpf_probe:func:(ffffffff9811b5f0) tv_sec=5
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hrtimer_nanosleep ([kernel.kallsyms])
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__x64_sys_nanosleep ([kernel.kallsyms])
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do_syscall_64 ([kernel.kallsyms])
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entry_SYSCALL_64 ([kernel.kallsyms])
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__GI___nanosleep (/usr/lib64/libc-2.26.so)
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rpl_nanosleep (/usr/bin/sleep)
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xnanosleep (/usr/bin/sleep)
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main (/usr/bin/sleep)
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__libc_start_main (/usr/lib64/libc-2.26.so)
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_start (/usr/bin/sleep)
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^C#
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Copyright (C) 2018 Red Hat, Inc., Arnaldo Carvalho de Melo <acme@redhat.com>
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*/
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#include <
bpf.h
>
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int
probe
(hrtimer_nanosleep, rqtp->tv_sec)(
void
*ctx,
int
err
,
long
sec
)
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{
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return
sec
== 5;
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}
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license
(GPL);
err
int int err
Definition:
5sec.c:44
sec
int int long sec
Definition:
5sec.c:45
bpf.h
license
license(GPL)
probe
int probe(hrtimer_nanosleep, rqtp->tv_sec)(void *ctx
examples
bpf
5sec.c
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