On 2015/7/7 20:33, Namhyung Kim wrote:
Hi,
On Tue, Jul 7, 2015 at 12:38 PM, Wang Nan <wangn...@huawei.com> wrote:
This patch allows passing perf's own PID to '--filter' by using
'$PERFPID'. This should be useful when system-widely capturing
tracepoints events.
Before this patch, when doing something like:
# perf record -a -e syscalls:sys_enter_write <cmd>
One could easily get result like this:
# perf report --stdio
...
# Overhead Command Shared Object Symbol
# ........ ....... .................. ....................
#
99.99% perf libpthread-2.18.so [.] __write_nocancel
0.01% ls libc-2.18.so [.] write
0.01% sshd libc-2.18.so [.] write
...
Where most events are generated by perf itself.
A shell trick can be done to filter perf itself out:
# cat << EOF > ./tmp
> #!/bin/sh
> exec perf record -e ... --filter="common_pid != \$\$" -a sleep 10
> EOF
# chmod a+x ./tmp
# ./tmp
However, doing so is user unfriendly.
This patch introduces '$PERFPID' placeholder to perf's filter. Now
user is allowed to do the above work with:
# perf record -e ... --filter='common_pid != $PERFPID' -a sleep 10
Instead, what about adding an option to do the same thing, like
--exclude-perf or something?
I thought this idea. Please see one of my previous email:
http://lkml.kernel.org/r/559b3cc3.2030...@huawei.com
This patch gives user full control of their filters. They can create
filters like 'common_pid == $PERFPID' to profile perf itself, or use it
in some complex expressions.
But if most of you like adding new option, I can post a v3 with
'--exclude-perf' added. Yes, the code of it can be much simpler than
this patch.
Thanks,
Namhyung
This patch adds the variable replacement code to perf_evsel__apply_filter(),
before PERF_EVENT_IOC_SET_FILTER ioctl, so not only 'perf record', all
subcommands which uses filter can utilize $PERFPID.
Andi Kleen sent a similar patch at 2014, but wasn't applied, the
reason is not clear.
Signed-off-by: Wang Nan <wangn...@huawei.com>
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