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    SubjectRe: accept() improvements for rt signals
    Dean Gaudet wrote:
    >
    > where's ingo? shouldn't he be jumping in here telling us syscall overhead
    > is some impressively tiny number of cycles which is bare noise above the
    > L1/L2 cache sloshing we'll see at scale? :) after all, we're talking

    fwiw here int80 syscall overhead is ~298 cycles (that's getpid latency),
    sysenter reduces it by ~130 cycles.

    > about servers with 4k+ sockets, and alan cox tells us to budget about 23kb
    > of memory per socket -- that's almost 100Mb of RAM... makes me wonder if
    > combining syscalls is worth the complexity.

    it isn't. at least not for uncommon ones like accept/close; if the
    few hundred cycles make a real difference you have other problems
    anyway. [ignoring benchmark #s]

    > out of curiosity, has the fast syscall and fast gettimeofday stuff with
    > the nifty kernel-supplied code page made it into the kernel/glibc/etc?

    not that i know of. it's not trivial stuff; you'll probably end up
    redesigning a large part of the current syscall code (if it's to be
    reasonably clean). i actually now have both sysenter and the magic
    sysentry page in this kernel, but i haven't merged them together
    yet :) (various reasons, like: it's not 2.4 stuff, i was kind of hoping
    the people who were mentioning amd syscall would produce something too
    (so i could be sure the abi worked for them too), there are a few unsolved
    issues etc.).


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