RE: Memory and CPU usage

["Howard Chu" <hyc@highlandsun.com>]

> -----Original Message-----
> From: Tony Earnshaw [mailto:tonni@billy.demon.nl]

> søn, 2003-02-16 kl. 19:47 skrev Howard Chu:

> > All the threads in
> > the world won't improve your concurrency once your I/O
> bandwidth (disk and
> > network) is saturated. And using too many threads will push
> you to the
> > saturation point sooner, because the increased memory usage
> will trigger
> > excessive paging/swapping (thrashing).
>
> Stupid question (RTFM), but how would I limit the number of threads?

slapd.conf(5) "threads 12" would limit to 12 max.

> > Some may be good, but more is not always better.
>
> Threads often have a habit of multiplying if they are not
> limited to any specific value.

True. Fortunately there is an enforced limit in slapd, but as others have
already commented, the default of 32 is too high for a lot of systems.

> > Threads don't come for free, and today they're not even "cheap".
>
> What's with "today?" RAM expensive? Or processor level 2 cache?

The oxymoron known as "lightweight processes" has become a very popular
vehicle for implementing threads. This is how Linux has always done it, and
it's how Solaris is doing it. Once you put thread scheduling into the kernel,
you've lost any pretense at "light weight" context switches.

> > As a sysadmin you need to understand the
> > limits of the machines you're working with.
>
> Absolutely.

> As far as T.'s "(?=undefined)" goes, where are we at here? Where does
> the "(?=undefined)" come from? From your explanation, it could be easy
> to deduce why his configuration didn't work. Did the "(?=undefined)"
> have anything to do with it? It doesn't seem so, to me.

This comes from trying to filter an attributeType that doesn't have a
matching rule defined. Thus, that element of the filter is undefined, and
doesn't contribute to the results of the search.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support