Messages in this thread | | | Date | Wed, 10 Nov 2004 11:01:45 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] VM routine fixes |
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David Howells <dhowells@redhat.com> wrote: > > Compound pages seem to be in some way tied to the TLB entry coverage sizes > available (for hugetlb), so it's not obvious that it's permitted to have > compound pages not of these sizes, and as I need to allocate arbitrary > sizes...
We've considered enabling compound pages permanently. We thought sparc64 might want that, and it simplifies coverage testing. But the conditionality has been left in for now as a microoptimisation.
> If I am correct about this, then the !MMU problem would still exist - just > with adjacent sets of compound pages rather than adjacent sets of pages.
Why _does_ !CONFIG_MMU futz around with page counts in such weird ways anyway? Why does it have requirements for higher-order pages which differ from !CONFIG_MMU?
If someone could explain the reasoning behind the current code, and the FRV enhancements then perhaps we could work something out.
> Compound pages might be nice, but they're overkill.
I don't expect they have significant performance overhead, because they'll only add cycles for higher-order pages. They're rare, and are already rather inefficient. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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