Re: [QUICKLIST 0/4] Arch independent quicklists V2

[Christoph Lameter]

On Tue, 13 Mar 2007, Andrew Morton wrote:

> > 1. We need to support other states of pages other than zeroed.
> 
> What does this mean?

pgd are not completely zeroed. They contain mappings that are always 
present. Thus the state is not a zeroed state.

> > 2. Prezeroing does not make much sense if a large portion of the
> >    page is being used. Performance is better if the whole page 
> >    is zeroed directly before use.Prezeroing only makes sense for sparse
> >    allocations like the page table pages.
> 
> This is not related to the above discussion.

Really? I definitely see the word prezeroing in the discussion.

> > I already tried that 3 years ago and there was *no* benefit for usual
> > users of the a page allocator. The advantage exists only if a small
> > portion of the page is used. F.e. For one cacheline there was a 4x 
> > improvement. See lkml archives for prezeroing.
> 
> Unsurprised.  Were non-temporal stores tried?

Yes with no material change. The work lead to making ia64 use non 
temporal stores for spin unlock but it was not useful for prezeroing.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/