linux-kernel - Re: slub-i386-support.patch

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Message-ID: <20070511074336.GS19966@holomorphy.com>
Date:	Fri, 11 May 2007 00:43:36 -0700
From:	William Lee Irwin III <wli@...omorphy.com>
To:	Christoph Lameter <clameter@....com>
Cc:	Hugh Dickins <hugh@...itas.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <ak@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: slub-i386-support.patch

On Thu, 10 May 2007, William Lee Irwin III wrote:
>> Looking more closely at it, the entire attempt to avoid struct page
>> pointers is far beyond pointless. The freeing functions unconditionally
>> require struct page pointers to either be passed or computed and the
>> allocation function's virtual address it returns as a result is not
>> directly usable. The callers all have to do arithmetic on the result.
>> One might as well stash precomputed pfn's (if not paddrs) and vaddrs in
>> page->private and page->mapping, chain them with ->lru (use only .next
>> if you care to stay singly-linked), and handle struct page pointers

On Thu, May 10, 2007 at 10:09:32PM -0700, Christoph Lameter wrote:
> Well then you'd have to rewrite the existing ways of fiddling with page 
> structs. This way all is clear and you fiddle as you want. It just works. 
> Could we get this in? You acked it once already?

I guess I can say I'm microoptimizing things by getting rid of the
lock. I can also do without mucking with fields in the page or
generation numbers given a method of dumping the entire cache for such
catastrophic reorganizations, which is actually better because it makes
change_page_attr() and vmalloc_sync() bear the entire cost, apart from
the loss of the cache in their aftermath. I'll post one of those two in
a follow-up.


-- wli
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