Re: [PATCH 4 of 4] Introduce aio system call submission and completion system calls

On Wednesday 31 January 2007 18:15, Zach Brown wrote:

On Jan 31, 2007, at 12:58 AM, Andi Kleen wrote:

Do you have any numbers how this compares cycle wise to just doing
clone+syscall+exit in user space?

Not yet, no. Release early, release often, and all that. I'll throw
something together.

So what was the motivation for doing this then? It's only point
is to have smaller startup costs for AIO than clone+fork without
fixing the VFS code to be a state machine, right?

I'm personally unclear if it's really less work to teach a lot of
code in the kernel about a new thread abstraction than changing VFS.

Your patches don't look that complicated yet but you openly
admitted you waved away many of the more tricky issues (like
signals etc.) and I bet there are yet-unknown side effects
of this too that will need more changes.

I would expect a VFS solution to be the fastest of any at least.

I'm not sure the fibrils thing will be that much faster than
a possibly somewhat fast pathed for this case clone+syscall+exit.

-Andi
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