----- "Maxim Dounin" <mdou...@mdounin.ru> wrote:
Hello!
On Thu, Mar 12, 2009 at 06:40:13PM -0700, Merlin wrote:
On Thu, Mar 12, 2009 at 4:51 PM, Michael Baudino <
mich...@acrelec.com> wrote:
Hi C.
Participating in the SoC is a definitively good idea.
What about implementing async disk IO ?
What's wrong with aio_write() and aio_read()?
Well, you really want to hear? There is a couple of issues:
1. There is no good standard method of notification. Per POSIX
it's uses signals to notify process about completed operations.
Under FreeBSD notifications is possible over kqueue, and probably
other OSes have something too, but it's anyway will require some
non-trivial porting.
Here I disagree: linux kernel supports notification via eventfd since 2.6.18.
eventfd syscall is available as of glibc 2.8, which is a part of e.g. ubuntu
intrepid distribution.
Personally I've tested this interface and it looks fine to me.
2. It's usually implemented as a thread pool within OS kernel (at
least FreeBSD and Linux implementations AFAIK), and usually have
some limits administrator should be aware of (including maximum
number of io requests system may queue).
It is unclear whether kernel thread pool is a disadvantage or not. I don't think
it is reasonable to use disk AIO as a primary mean to serve files, I think it
won't make server faster than while using sendfile, but AIO could be serious
boost for large out-of-cache files, because it eliminates blocking.
With such considerations kernel thread pool doesn't seem to be a big hassle.
38 messages in ru.sysoev.nginxRe: Nginx - Google Summer of Code ideas
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