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SubjectRe: [PATCH 2 of 4] Introduce i386 fibril scheduling
On Tue, Feb 06, 2007 at 03:56:14PM -0800, Davide Libenzi wrote:
> Async syscall submissions are a _one time_ things. It's not like a live fd
> that you can push inside epoll and avoid the multiple O(N) passes.
> First of all, the amount of syscalls that you'd submit in a vectored way
> are limited. They do not depend on the total number of connections, but on

I regularly see apps that want to submit 1000 I/Os at once.
Every submit. But it's all against one or two file descriptors. So, if
you return to userspace, they have to walk all 1000 async_results every
time, just to see which completed and which didn't. And *then* go wait
for the ones that didn't. If they just wait for them all, they aren't
spinning cpu on the -EASYNC operations.
I'm not saying that "don't return a completion if we can
non-block it" is inherently wrong or not a good idea. I'm saying that
we need a way to flag them efficiently.

Joel

--

Life's Little Instruction Book #80

"Slow dance"

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127
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