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    SubjectRe: [RFC bpf-next 0/4] bpf: Speed up symbol resolving in kprobe multi link
    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!

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