Re: [00/17] Large Blocksize Support V3

From: Christoph Lameter
Date: Thu Apr 26 2007 - 02:46:28 EST

On Thu, 26 Apr 2007, Nick Piggin wrote:

> Yeah. IMO anti-fragmentation and defragmentation is the hack, and we
> should stay away from higher order allocations whenever possible.

Right and we need to create series of other approaches that we then label
"non-hack" to replace it.

> Hardware is built to handle many small pages efficintly, and I don't
> understand how it could be an SGI-only issue. Sure, you may have an
> order of magnitude or more memory than anyone else, but even my lowly
> desktop _already_ has orders of magnitude more pages than it has TLB
> entries or cache -- if a workload is cache-nice for me, it probably
> will be on a 1TB machine as well, and if it is bad for the 1TB machine,
> it is also bad on mine.

There have been numbers of people that have argued the same point. Just
because we have developed a way of thinking to defend our traditional 4k
values does not make them right.

> If this is instead an issue of io path or reclaim efficiency, then it
> would be really nice to see numbers... but I don't think making these
> fundamental paths more complex and slower is a nice way to fix it
> (larger PAGE_SIZE would be, though).

The code paths can stay the same. You can switch CONFIG_LARGE pages off
if you do not want it and it is as it was.

If you would have a look the patches: The code is significantly cleanup
and easier to read.
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