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    SubjectRe: dnotify/inotify and vfs questions
    On Thu, 2005-08-25 at 15:57 +0100, Jamie Lokier wrote:
    > Ian Campbell wrote:
    > > On Tue, 2005-08-23 at 16:23 +0100, Jamie Lokier wrote:
    > > > <receive some request>...
    > > > if (any_dnotify_or_inotify_events_pending) {
    > > > read_dnotify_or_inotify_events();
    > > > if (any_events_related_to(file)) {
    > > > store_in_userspace_stat_cache(file, stat(file));
    > > > }
    > > > }
    > > > stat_info = lookup_userspace_stat_cache(file);
    > > >
    > > > Now that's a silly way to save one system call in the fast path by itself.
    > >
    > > I'm not that familiar with inotify internals but doesn't
    > > read_dnotify_or_inotify_events() or
    > > any_dnotify_or_inotify_events_pending() involve a syscall?
    >
    > The fast path is just any_dnotify_or_inotify_events_pending: there
    > aren't any relevant events pending in the fast path.
    [snip]
    > As I explained in the previous mail, all this is absolutely pointless
    > to save one system call. It's a lot of work for negligable gain.
    >
    > The point is when it saves lots of calls and userspace logic together,
    > for things like web page templates and compiled programs, which depend
    > on many files which can be revalidated in a small number of operations.

    Thanks for the explaination.

    Ian.
    --
    Ian Campbell
    Current Noise: Iron Maiden - Prodigal Son

    Fay: The British police force used to be run by men of integrity.
    Truscott: That is a mistake which has been rectified.
    -- Joe Orton, "Loot"

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