FreeLists / haiku-development / [haiku-development] Re: heap freelist problem?

["Michael Lotz" <mmlr@xxxxxxxx>]

Hi Jonas

> > It would be possible to check if a whole chunk is 
> > now in the freelist and all the allocated pages could
> > be freed now, but this would require some algorithms
> > I doubt will be implemented since 
> > the allocator is going to be replaced anyway...
> 
> Would it be worthwhile having a kernel thread or some 
> other not so very periodic routine to try (for as long as we
> want the PARANOID_KFREE) to remove empty bins?

If we didn't intend to throw away the allocator it would certainly be 
the way to go.

> I don't think the routine to find empty bins would have to be
> complex, and I'm guessing its thread, or whatever, could be
> scheduled with a frequency of seconds or less.

Sure, but that would give some quite "strange" times where closing apps 
sometimes results in a slowdown for a second or so and sometimes it 
doesn't. Not a huge problem, just a possible irritation.

> As an alternative to directly removing bins, one could have
> them age and convert them to larger element bins over time, 
> with fewer elements and thus shorter freelists, and eventually
> remove the expired, empty 2048 byte size bins, given a 4kb
> page size. Would that make sense?

Well that gets kinda complex now ;-). Again, it could certainly be 
implemented, but since a) the allocator will be replaced and b) having 
long freelists around doesn't really hurt when we eventually turn off 
PARANOID_KFREE, I just don't see it as a particularly usful thing to 
spend time on.

I am going to take a look at simply sorting the freelists which should 
have no real performance impact and speed up the lookup considerably. 
That will probably be a good enough fix for the current situation.

Regards
Michael