Re: [9fans] Calling vac from C

[Ben Calvert <ben@flyingwalrus.net>]

On Fri, 20 Feb 2009, erik quanstrom wrote:

> On Fri Feb 20 11:18:41 EST 2009, uriel99@gmail.com wrote:
>> One of the main costs of dynamic linking is making fork much slower.
>> Even on linux statically linked binaries fork a few magnitude orders
>> faster than dynamically linked ones.
>>
>> The main source of anti-fork FUD turns out to be the alleged
>> 'solution' to a problem that didn't exist until the geniuses at Sun
>> decided dynamic linking was such a wonderful idea.
>
> very generally, i agree with the direction of your
> post.  but i do remember things a bit differently.
>
> iirc, this went the other way 'round.  fork itself
> was very expensive on sun hardware in the early
> 90s if one had some memory mapped.  sun mmus
> had issues.  i benchmarked a vax 11/780 vs a sun
> 670mp.  the 4x50mhz 670mp was scheduled to replace the
> 1x5mhz (?) vaxen.  the vax forked maybe 10x faster when no
> memory was allocated.  however, when a moderate
> amount of memory was allocated, the vax pounded
> the sun by many (3, i think) of magnitude.

about 5 years ago i took a class on performance tuning Solaris.

The instructor claimed that fork was expensive because accounting is never really turned off, just piped to /dev/null.  there is no accounting overhead for threads.

I never bothered to verify this, but now that this comes up, I'd tempted.

> - erik