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    SubjectRe: aio-core why not using SuS? [Re: [rfc] aio-core for 2.5.29 (Re: async-io API registration for 2.5.29)]
    On Fri, Aug 16, 2002 at 01:54:59AM +0200, Andrea Arcangeli wrote:
    > the window a kernel window inside a preempt_disable and a __cli() will
    > have a goodness effect in a number of cases, but I don't think it
    > matters significantly because you still need some gettimeofday in
    > userspace (or clock_gettime if that matters, clock_gettime infact is
    > even worse than gettimeofday due its certainly lower resolution).

    Yeah, I've come full circle back to the relative timeout point of view.
    By grabbing a copy of jiffies at the beginning of the function the race
    with preempt can be avoided.

    > Now reading the SuS specifications I also like less and less our current
    > kernel API of this sumbit_io, the SuS does exactly what I suggested
    > originally that is aio_read/aio_write/aio_fsync as separate calls. So
    > the merging effect mentioned by Ben cannot be taken advantage of by the
    > kernel anyways because userspace will issue separate calls for each
    > command.

    Read it again. You've totally missed lio_listio. Also keep in mind what
    happens with 4G/4G split for x86 which are needed to address the kernel
    virtual memory starvation issues.

    -ben
    --
    "You will be reincarnated as a toad; and you will be much happier."
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