Re: SLAB allocator now the default.

[David Leimbach <leimy2k@xxxxxxx>]

On Sep 28, 2003, at 9:22 AM, Hiten Pandya wrote:

> Matthew Dillon wrote:
>
> >     The slab allocator is now the default.  The NO_KMEM_MAP and
> >     USE_SLAB_ALLOCATOR options have been removed.
> >     USE_KMEM_MAP and NO_SLAB_ALLOCATOR options have temporarily been 
> > added,
> >     but these too will be removed (along with the old malloc and 
> > kmem_map
> >     code) in about a week.

Hiten,

> 	Matt,
>
> 	I haven't looked at the Slab-alloc code recently, but I am
> 	wondering if you are planning to remove the power-of-2 alignment
> 	stuff out of malloc()?

Doesn't power of two alignment make it easier on some CPUs internally 
to access
data?  If a person wanted to access a word overlapping two word's 
alignment would it
not take two bus accesses to get that data [or two cache reads... what 
have  you]

Do the benefits of not having power of two alignment outweigh this?



> 	From the many papers I have been reading in the last couple of
> 	weeks, it seems that power-of-2 alignment seems to cause a lot
> 	of performance degradation in SMP cases, and cache issues.
>
> 	A good example of this demonstration is in Bonwick's papers.

> 	I understand this would be quite a lengthy and tedious procedure
> 	but it is something that I have been wondering.
>
> 	Regards,
>
> --
> Hiten Pandya
> hmp@xxxxxxxxxxxxx