Messages in this thread | | | Date | Tue, 10 Jun 2008 23:16:42 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH -mm 13/25] Noreclaim LRU Infrastructure |
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On Wed, 11 Jun 2008 14:09:15 +0900 Paul Mundt <lethal@linux-sh.org> wrote:
> On Tue, Jun 10, 2008 at 02:33:34PM -0700, Andrew Morton wrote: > > On Tue, 10 Jun 2008 15:37:02 -0400 > > Rik van Riel <riel@redhat.com> wrote: > > > > > On Tue, 10 Jun 2008 12:17:23 -0700 (PDT) > > > Christoph Lameter <clameter@sgi.com> wrote: > > > > > > > On Sun, 8 Jun 2008, Andrew Morton wrote: > > > > > > > > > And it will take longer to get those problems sorted out if 32-bt > > > > > machines aren't even compiing the new code in. > > > > > > > > The problem is going to be less if we dependedn on > > > > CONFIG_PAGEFLAGS_EXTENDED instead of 64 bit. This means that only certain > > > > 32bit NUMA/sparsemem configs cannot do this due to lack of page flags. > > > > > > > > I did the pageflags rework in part because of Rik's project. > > > > > > I think your pageflags work freed up a number of bits on 32 > > > bit systems, unless someone compiles a 32 bit system with > > > support for 4 memory zones (2 bits ZONE_SHIFT) and 64 NUMA > > > nodes (6 bits NODE_SHIFT), in which case we should still > > > have 24 bits for flags. > > > > > > Of course, having 64 NUMA nodes and a ZONE_SHIFT of 2 on > > > a 32 bit system is probably total insanity already. I > > > suspect very few people compile 32 bit with NUMA at all, > > > except if it is an architecture that uses DISCONTIGMEM > > > instead of zones, in which case ZONE_SHIFT is 0, which > > > will free up space too :) > > > > Maybe it's time to bite the bullet and kill i386 NUMA support. afaik > > it's just NUMAQ and a 2-node NUMAish machine which IBM made (as400?) > > > > arch/sh uses NUMA for 32-bit, I believe. But I don't know what its > > maximum node count is. The default for sh NODES_SHIFT is 3. > > In terms of memory nodes, systems vary from 2 up to 16 or so. It gets > gradually more complex in the SMP cases where we are 3-4 levels deep in > various types of memories that we expose as nodes (ie, 4-8 CPUs with a > dozen different memories or so at various interconnect levels).
Thanks.
Andi has suggested that we can remove the node-ID encoding from page.flags on x86 because that info is available elsewhere, although a bit more slowly.
<looks at page_zone(), wonders whether we care about performance anyway>
There wouldn't be much point in doing that unless we did it for all 32-bit architectures. How much trouble would it cause sh?
> As far as testing goes, it's part of the regular build and regression > testing for a number of boards, which we verify on a daily basis > (although admittedly -mm gets far less testing, even though that's where > most of the churn in this area tends to be).
Oh well, that's what -rc is for :(
It would be good if someone over there could start testing linux-next. Once I get my act together that will include most-of-mm anyway.
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