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

[Ingo Molnar <mingo@elte.hu>]

* Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:

> > does that work for you?
> 
> Yes, -fomit-frame-point make the deal.
> 
> In average, threadlet runs as fast as epoll.

yeah.

> Just because there are _no_ rescheduling in that case.

in my test it was 'little', not 'no'. But yes, that's exactly my point: 
we can remove the nonblock hackeries from event loops and just 
concentrate on making it schedule in less than 10-20% of the cases. Even 
a relatively high 10-20% rescheduling rate is hardly measurable with 
threadlets, while it gives a 10%-20% regression (and possibly bad 
latencies) for the pure epoll/kevent server.

and such a mixed technique is simply not possible with ordinary 
user-space threads, because there it's an all-or-nothing affair: either 
you go fully to threads (at which point we are again back to a fully 
threaded design, now also saddled with event loop overhead), or you try 
to do user-space threads, which Just Make Little Sense (tm).

so threadlets remove the biggest headache from event loops: they dont 
have to be '100% nonblocking' anymore. No O_NONBLOCK overhead, no 
complex state machines - just handle the most common event type via an 
outer event loop and keep the other 99% of server complexity in plain 
procedural programming. 1% of state-machine code is perfectly 
acceptable.

	Ingo