Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

Davide Libenzi
2007-02-22T19:46:50Z

On Thu, 22 Feb 2007, Evgeniy Polyakov wrote:

> > maybe it will, maybe it wont. Lets try? There is no true difference
> > between having a 'request structure' that represents the current state
> > of the HTTP connection plus a statemachine that moves that request
> > between various queues, and a 'kernel stack' that goes in and out of
> > runnable state and carries its processing state in its stack - other
> > than the amount of RAM they take. (the kernel stack is 4K at a minimum -
> > so with a million outstanding requests they would use up 4 GB of RAM.
> > With 20k outstanding requests it's 80 MB of RAM - that's acceptable.)
>
> I tried already :) - I just made a allocations atomic in tcp_sendmsg() and
> ended up with 1/4 of the sends blocking (I counted both allocation
> failure and socket queue overflow). Those 20k blocked requests were
> created in about 20 seconds, so roughly saying we have 1k of thread
> creation/freeing per second - do we want this?

A dynamic pool will smooth thread creation/freeing up by a lot.
And, in my box a *pthread* create/free takes ~10us, at 1000/s is 10ms, 1%.
Bad, but not so aweful ;)
Look, I'm *definitely* not trying to advocate the use of async syscalls for
network here, just pointing out that when we're talking about threads,
Linux does a pretty good job.

- Davide