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    SubjectRe: [PATCH 03/10] jump label v11: base patch
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    On Tue, 2010-09-21 at 19:36 +0200, Andi Kleen wrote:
    > > On Tue, 2010-09-21 at 16:41 +0200, Andi Kleen wrote:
    > >> >
    > >> > So there are ~150 tracepoints, but this code is also being proposed
    > >> for
    > >> > use with 'dynamic debug' of which there are > 1000, and I'm hoping for
    > >> > more users moving forward.
    > >>
    > >> Even 1000 is fine to walk, but if it was sorted a binary search
    > >> would be much faster anyways. That is then you would still
    > >> need to search for each module, but that is a relatively small
    > >> number (< 100)
    > >
    > > xfs has > 100 tracepoints
    >
    > Doesn

    I suppose you were missing a 't'.

    Anyway:

    $ find fs/xfs/ -name "*.c" ! -type d | xargs grep "[ ^I]trace_" | wc -l
    313

    The jump label occurs at the calling sight, not for defined tracepoints
    (which can be used in multiple places).

    Also take a look at fs/xfs/linux-2.6/xfs_trace.h, you will be surprised.


    > >
    > >>
    > >> > Also, I think the hash table deals nicely with modules.
    > >>
    > >> Maybe but it's also a lot of code. And it seems to me
    > >> that it is optimizing the wrong thing. Simpler is nicer.
    > >
    > > I guess simplicity is in the eye of the beholder. I find hashes easier
    > > to deal with than binary searching sorted lists. Every time you add a
    > > tracepoint, you need to resort the list.
    >
    > The only time you add one is when you load a module, right? When you do
    > that you only sort the section of the new module.

    And on removing a module.

    >
    > > Hashes are much easier to deal with and scale nicely. I don't think
    > > there's enough rational to switch this to a binary list.
    >
    > Well problem is that the code is very complicated today. I suspect
    > this could be done much simpler if it wasn't so overengin
    >

    Perhaps it can be cleaned up. But I have no issues with it now, and
    using a hash (basic data structures 101) is not where the complexity
    comes in.

    -- Steve




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