lkml.org 
[lkml]   [2007]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3
    On Wed, 28 Feb 2007, Ingo Molnar wrote:

    >
    > * Davide Libenzi <davidel@xmailserver.org> wrote:
    >
    > > Why can't aio_* be implemented with *simple* (or parallel/unrelated)
    > > syscall submit w/out the burden of a complex, limiting and heavy API
    >
    > there are so many variants of what people think 'asynchronous IO' should
    > look like - i'd not like to limit them. I agree that once a particular
    > syslet script becomes really popular, it might (and should) in fact be
    > pushed into a separate system call.
    >
    > But i also agree that a one-shot-syscall sys_async() syscall could be
    > done too - for those uses where only a single system call is needed and
    > where the fetching of a single uatom would be small but nevertheless
    > unnecessary overhead. A one-shot async syscall needs to get /8/
    > parameters (the syscall nr is the seventh parameter and the return code
    > of the nested syscall is the eighth). So at least two parameters will
    > have to be passed in indirectly and validated, and 32/64-bit compat
    > conversions added, etc. anyway!

    At this point, given how threadlets can be easily/effectively dispatched
    from userspace, I'd argue the presence of either single/parallel or syslet
    submission altogether. Threadlets allows you to code chains *way* more
    naturally than syslets, and since they basically are like functions calls
    in the fast path, they can be used even for single/parallel submissions.
    No compat code required (ok, besides the trivial async_wait).
    My point is, the syslet infrastructure is expensive for the kernel in
    terms of compat, and extra code added to handle the cond/jumps/etc. Is
    also non-trivial to use from userspace. Are those big performance
    advantages there to justify its existence? I doubt that the price of a
    sysenter is a lot bigger than a atom decoding, but I'm looking forward in
    being proven wrong by real life performance numbers ;)



    - Davide


    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-02-28 17:19    [W:3.528 / U:1.504 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site