On Thu, Apr 07, 2022 at 02:52:20PM +0200, Jiri Olsa wrote:
> hi,
> sending additional fix for symbol resolving in kprobe multi link
> requested by Alexei and Andrii [1].
>
> This speeds up bpftrace kprobe attachment, when using pure symbols
> (3344 symbols) to attach:
>
> Before:
>
> # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
> ...
> 6.5681 +- 0.0225 seconds time elapsed ( +- 0.34% )
>
> After:
>
> # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
> ...
> 0.5661 +- 0.0275 seconds time elapsed ( +- 4.85% )
>
>
> There are 2 reasons I'm sending this as RFC though..
>
> - I added test that meassures attachment speed on all possible functions
> from available_filter_functions, which is 48712 functions on my setup.
> The attach/detach speed for that is under 2 seconds and the test will
> fail if it's bigger than that.. which might fail on different setups
> or loaded machine.. I'm not sure what's the best solution yet, separate
> bench application perhaps?
are you saying there is a bug in the code that you're still debugging?
or just worried about time?
I think it's better for it to be a part of selftest.
CI will take extra 2 seconds to run.
That's fine. It's a good stress test.
> - copy_user_syms function potentially allocates lot of memory (~6MB in my
> tests with attaching ~48k functions). I haven't seen this to fail yet,
> but it might need to be changed to allocate memory gradually if needed,
> do we care? ;-)
replied in the other email.
Thanks for working on this!
