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    SubjectRe: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3
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    > It is not a TUX anymore - you had 1024 threads, and all of them will be
    > consumed by tcp_sendmsg() for slow clients - rescheduling will kill a
    > machine.

    I think it's time to make a split in what "context switch" or
    "reschedule" means...

    there are two types of context switch:

    1) To a different process. This means teardown of the TLB, going to a
    new MMU state, saving FPU state etc etc etc. This is obviously quite
    expensive

    2) To a thread of the same process. No TLB flush no new MMU state,
    effectively all it does is getting a new task struct on the kernel side,
    and a new ESP/EIP pair on the userspace side. If there is FPU code
    involved that gets saved as well.

    Number 1 is very expensive and that is what is really worrying normally;
    number 2 is a LOT lighter weight, and while Linux is a bit heavy there,
    it can be made lighter... there's no fundamental reason for it to be
    really expensive.

    --
    if you want to mail me at work (you don't), use arjan (at) linux.intel.com
    Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

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