<p></p>
<p dir="auto">Hello</p>
<p dir="auto">I am stracing apache with this procedure:</p>
<pre><code>strace -ff -s 512 -o /space/OTHERS/apache_strace -r -T -p 7124 &> /dev/null &
apachectl graceful
sleep 20
kill %1
</code></pre>
<p dir="auto">But in some trace I get:</p>
<pre><code>     0.000008 semop(9764864, [{sem_num=0, sem_op=-1, sem_flg=SEM_UNDO}], 1) = 0 <9.685337>
     0.000022 epoll_wait(55, [{events=EPOLLIN, data={u32=450864712, u64=140480241182280}}], 3, 10000) = 1 <0.046295>
</code></pre>
<p dir="auto">How the relative timestamp of epoll_wait can be 0.000022 while the syscall time of semop is 9.685337 ?</p>
<pre><code># src/strace -V
strace -- version 5.16
Copyright (c) 1991-2022 The strace developers <https://strace.io>.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Optional features enabled: no-m32-mpers no-mx32-mpers
</code></pre>
<p dir="auto">Any idea ?</p>
<p dir="auto">note: same with <code>-tt</code> options</p>
<pre><code>20:37:49.050065 (+     0.000012) semop(9928704, [{sem_num=0, sem_op=-1, sem_flg=SEM_UNDO}], 1) = 0 <5.030807>
20:37:54.080941 (+     0.000039) epoll_wait(55, [{events=EPOLLIN, data={u32=450864760, u64=140480241182328}}], 3, 10000) = 1 <0.136024>
</code></pre>

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