Re: threadlets as 'naive pool of threads', epoll, some measurements

Evgeniy Polyakov
2007-02-26T14:34:21Z

On Mon, Feb 26, 2007 at 01:50:54PM +0100, Ingo Molnar (mingo@elte.hu) wrote:
> > I feared _ONLY_ situation when thousands of thereads are eating my
> > brain - so case when 161 threads are running simultanesoulsy is not
> > that bad compared to what micro-design can do (of its best/worst) at
> > all!
>
> even with ten thousand threads it is still pretty fast. Certainly not
> '10 times slower' as you claimed. And it takes only a single, trivial
> outer event loop to lift it up to the performance levels of a pure event
> based server.

I did not claim that it will be 10 times slower, I said that it will be
slower, my '10 times slower', which are actually '15% of hte total time'
is a reply to your 'fast as sync' model, no need to repaing the picture :)

> conclusion: currently i dont see a compelling need for the kevents
> subsystem. epoll is a pretty nice API and it covers most of the event
> sources and nicely builds upon our existing poll() infrastructure.
>
> furthermore, i very much contest your claim that a high-performance,
> highly scalable webserver needs a kevent+nonblock design. Even if i
> ignore all the obvious usability and maintainance-cost advantages of
> threadlets.

Ok, I see your point, you insult something you did not ever try to
understand, that is your right.

> > So, caching is good - threadlets do not spawn a new thread, kevent
> > returns immediately, but in case of things are not that shine -
> > threadlets spawnd a new thread, while kevent process next request or
> > waits for all completed.
>
> no. Please read the evserver_threadlet.c code. There's no kevent in
> there. There's no epoll() in there. All that you can see there is the
> natural behavior of pure threadlets. And it's not a workload /I/ picked
> for threadlets - it is a workload, filesize, parallelism level and
> request handling function /you/ picked for "event-servers".

I know that there is no kevents there, that would be really strange if
you would test it in your environment after all that empty kevent
releases.

Enough, you say micro-thread design is superior - ok, that is your
point.

> Ingo

--
Evgeniy Polyakov