Re: [PATCH 20/20] Get rid of the concept of hot/cold page freeing

[Christoph Lameter]

On Thu, 26 Feb 2009, Mel Gorman wrote:

> > I tried the general use of a pool of zeroed pages back in 2005. Zeroing
> > made sense only if the code allocating the page did not immediately touch
> > the cachelines of the page.
>
> Any feeling as to how often this was the case?

Not often enough to justify the merging of my patches at the time. This
was publicly discussed on lkml:

http://lkml.indiana.edu/hypermail/linux/kernel/0503.2/0482.html

> Indeed, any gain if it existed would be avoiding zeroing the pages used
> by userspace. The cleanup would be reducing the amount of
> architecture-specific code.
>
> I reckon it's worth an investigate but there is still other lower-lying
> fruit.

I hope we can get rid of various ugly elements of the quicklists if the
page allocator would offer some sort of support. I would think that the
slow allocation and freeing behavior is also a factor that makes
quicklists advantageous. The quicklist page lists are simply a linked list
of pages and a page can simply be dequeued and used.


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