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

From: Davide Libenzi
Date: Fri Feb 23 2007 - 12:43:40 EST

On Fri, 23 Feb 2007, Evgeniy Polyakov wrote:

> On Thu, Feb 22, 2007 at 11:46:48AM -0800, Davide Libenzi (davidel@xxxxxxxxxxxxxxx) wrote:
> >
> > 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.
> If we are going to create 1000 threads each second, then it is better to
> preallocate them and queue a work to that pool - like syslets did with
> syscalls, but not ulitimately create a new thread just because it is not
> that slow.

We do create a pool indeed, as I said in the opening of my asnwer. The
numbers I posted was just to show that thread creation/destroy is pretty
fast, but that does not justify it as a design choice.

> All such micro-thread designs are especially good in the case when
> 1. switching is _rare_ (very)
> 2. programmer does not want to create complex model to achieve maximum
> performance
> Disk (cached) IO definitely hits first entry and second one is there for
> advertisements and fast deployment, but overall usage of the
> asynchronous IO model is not limited to the above scenario, so
> micro-threads definitely hit own niche, but they can not cover all usage
> cases.

You know, I read this a few times, but I still don't get what your point
is here ;) Are you talking about micro-thread design in the kernel as for
kthreads usage for AIO, or about userspace?

- Davide

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