a9f4c6c999
That is a 'struct timespec' passed from userspace to the kernel as we
can see with a system wide syscall tracing:
root@number:~# perf trace -e nanosleep
0.000 (10.102 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
38.924 (10.077 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
100.177 (10.107 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
139.171 (10.063 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
200.603 (10.105 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
239.399 (10.064 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
300.994 (10.096 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
339.584 (10.067 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
401.335 (10.057 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
439.758 (10.166 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
501.814 (10.110 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
539.983 (10.227 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
602.284 (10.199 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
640.208 (10.105 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
702.662 (10.163 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
740.440 (10.107 ms): podman/2195174 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
802.993 (10.159 ms): podman/9150 nanosleep(rqtp: { .tv_sec: 0, .tv_nsec: 10000000 }) = 0
^Croot@number:~# strace -p 9150 -e nanosleep
If we then use the ptrace method to look at that podman process:
root@number:~# strace -p 9150 -e nanosleep
strace: Process 9150 attached
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=10000000}, NULL) = 0
^Cstrace: Process 9150 detached
root@number:~#
With some changes we can get something closer to the strace output,
still in system wide mode:
root@number:~# perf config trace.show_arg_names=false
root@number:~# perf config trace.show_duration=false
root@number:~# perf config trace.show_timestamp=false
root@number:~# perf config trace.show_zeros=true
root@number:~# perf config trace.args_alignment=0
root@number:~# perf trace -e nanosleep --max-events=10
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/2195174 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
podman/9150 nanosleep({ .tv_sec: 0, .tv_nsec: 10000000 }, NULL) = 0
root@number:~#
root@number:~# perf config
trace.show_arg_names=false
trace.show_duration=false
trace.show_timestamp=false
trace.show_zeros=true
trace.args_alignment=0
root@number:~# cat ~/.perfconfig
# this file is auto-generated.
[trace]
show_arg_names = false
show_duration = false
show_timestamp = false
show_zeros = true
args_alignment = 0
root@number:~#
This will not get reused by any other syscall as nanosleep is the only
one to have as its first argument a 'struct timespec" pointer argument
passed from userspace to the kernel:
root@number:~# grep timespec /sys/kernel/tracing/events/syscalls/sys_enter_*/format | grep offset:16
/sys/kernel/tracing/events/syscalls/sys_enter_nanosleep/format: field:struct __kernel_timespec * rqtp; offset:16; size:8; signed:0;
root@number:~#
BTF based pretty printing will simplify all this, but then lets just get
the low hanging fruits first.
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/Zbq72dJRpOlfRWnf@kernel.org/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.