Re: [patch 0/4] mm: de-skew page refcount

[Nick Piggin]

On Wed, Jan 18, 2006 at 11:27:13AM -0800, Linus Torvalds wrote:
> 
> 
> On Wed, 18 Jan 2006, Nick Piggin wrote:
> > 
> > > So I disagree with this patch series. It has real downsides. There's a 
> > > reason we have the offset.
> > 
> > Yes, there is a reason, I detailed it in the changelog and got rid of it.
> 
> And I'm not applying it. I'd be crazy to replace good code by code that is 
> objectively _worse_.
> 

And you're not? Damn.

> The fact that you _document_ that it's worse doesn't make it any better.
> 
> The places that you improve (in the other patches) seem to have nothing at 
> all to do with the counter skew issue, so I don't see the point.
> 

You know, I believe you're right. I needed the de-skewing patch for
something unrelated and it seemed that it opened the possibility for
the following optimisations (ie. because we no longer touch a page
after its refcount goes to zero).

But actually it doesn't matter that we might touch page_count, only
that we not clear PageLRU. So the enabler is simply moving the
TestClearPageLRU after the get_page_testone.

So I'll respin the patches without the de-skewing and the series
will become much smaller and neater.

> So let me repeat: WHY DID YOU MAKE THE CODE WORSE?
> 

You've never bothered me about that until now...

Thanks for the feedback!

Nick
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