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    SubjectRe: 2.6.18-rc2-mm1
    On Fri, 28 Jul 2006 10:17:44 +0200
    "Michal Piotrowski" <michal.k.k.piotrowski@gmail.com> wrote:

    > Matt, can you look at this?
    >
    > My hunt file shows me, that this patches are causing oops.
    > GOOD
    > #
    > #
    > task-watchers-task-watchers.patch
    > task-watchers-register-process-events-task-watcher.patch
    > task-watchers-refactor-process-events.patch
    > task-watchers-make-process-events-configurable-as.patch
    > task-watchers-allow-task-watchers-to-block.patch
    > task-watchers-register-audit-task-watcher.patch
    > task-watchers-register-per-task-delay-accounting.patch
    > task-watchers-register-profile-as-a-task-watcher.patch
    > task-watchers-add-support-for-per-task-watchers.patch
    > task-watchers-register-semundo-task-watcher.patch
    > task-watchers-register-per-task-semundo-watcher.patch
    > BAD

    Thanks for working that out.

    I've actually been thinking that we shouldn't proceed with those patches.

    They're a nice cleanup and make the kernel code _look_ better and I really
    like them because of this. But the cost is potentially significant. We
    replace N direct calls with a walk of a notifier chain, more than N
    indirect calls, demultiplexing at the other end and then a direct call.
    That's a significant amount of additional overhead to make the kernel
    source look nicer.

    Plus, ugly though it is, you can look at the current code and see what it's
    doing. With a notifier chain you have to grep around the tree and work out
    what might be hooking into the chain, which is harder.

    Finally, the consolidation into a notifier chain forces all the
    fork/exit/exec hooks into an one-size-fits-all model. What happens if one
    subsystem wants to hook in before exit_mmap() and another one wants to hook
    in after exit_mmap() (for example)?


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