Re: kvm aio wishlist
From: Avi Kivity
Date: Tue Nov 25 2008 - 11:54:48 EST
Ingo Molnar wrote:
Perhaps a variant of syslet, that is kernel-only, and does:
- always allocate a new kernel stack at io_submit() time, but not a
new thread
such a N:M threading design is a loss - sooner or later we arrive to a
point where people actually start using it and then we want to
load-balance and schedule these entities.
It's only N:M as long as its nonblocking. If it blocks it becomes 1:1
again. If it doesn't, it's probably faster to do things on the same
cache as the caller.
So i'd suggest the kthread based async engine i wrote for syslets. It
worked well and for kernel-only entities it schedules super-fast - it
can do up to 20 million events per second on a 16-way box i'm testing
on. The objections about syslets were not related to the scheduling of
it but were mostly about the userspace API/ABI: you dont have to use
that.
I'd love to have something :)
I guess any cache and latency considerations could be fixed if
- we schedule a syslet for the first time when the thread that launched
it exits to userspace
- we queue it on the current cpu's runqueue
In that case, for the nonblocking case syslets and fibrils would have
very similar performance.
--
error compiling committee.c: too many arguments to function
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