Re: Notebooks

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Wed, 19 Aug 1998 13:51:12 +0200 (MEST)

Linus Torvalds wrote:
>
>
> On Wed, 19 Aug 1998, Andi Kleen wrote:
> >
> > My theory is that it is caused by better cache line usage. In the bulk
> > transfer case most packets have the same size (device MTU), and then
> > the cache wasn't effectively used. slab fixes that. Also the other
> > sk_buff code has been simplified which should speed it up too.

> Hmmm.. Slab does cache-align the allocations, something that the
> original code didn't try to do. The old kmalloc() tried to be
> space-efficient even if it meant returning an allocation at even
> just a 4-byte boundary, which might have been a mistake.

Linus, the kmalloc I submitted to you back in '93 wasted a few bytes
to do the cache alignment. You changed it before releasing it.

You were a few years younger then, and I forgive you for not knowing
all the "cache alignment issues". (the "mistake"). To be honest, I
didn't expect much out of it either, but wasting at most a few extra
percent of memory seemed worth the gamble to me :-)

Roger. 

-- 
| The secret of success is sincerity.  Once you can |  R.E.Wolff@BitWizard.nl 
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