Thread (16 messages) 16 messages, 5 authors, 2012-10-24

Re: [PATCH v2] mm: thp: Set the accessed flag for old pages on access fault.

From: Will Deacon <hidden>
Date: 2012-10-24 09:35:32
Also in: linux-mm, lkml

On Tue, Oct 23, 2012 at 10:50:27PM +0100, Andrew Morton wrote:
On Tue, 23 Oct 2012 11:11:25 +0100
Will Deacon [off-list ref] wrote:
quoted
This patch ("mm: thp: Set the accessed flag for old pages on access fault")
doesn't depend on "ARM: mm: Transparent huge page support for LPAE systems"
because currently transparent huge pages cannot be enabled for ARM in
mainline (or linux-next). update_mmu_cache_pmd is only called from
mm/huge_memory.c, which depends on CONFIG_TRANSPARENT_HUGEPAGE=y.

As for the new huge_pmd_set_accessed function... there's a similar situation
for the do_huge_pmd_wp_page function: it's called from mm/memory.c but is
only defined in mm/huge_memory.c. Looks like the compiler optimises those
calls away because pmd_trans_huge and friends constant-fold to 0.
Ah, OK.

"mm: thp: Set the accessed flag for old pages on access fault" clashes
in a non-trivial way with linux-next changes, due to the sched-numa
changes (sigh).  This is a problem for me, because I either need to
significantly alter your patch (so it isn't applicable to mainline) or
I need to stage your patch ahead of linux-next, then fix up linux-next
every day after I've pulled and re-merged it.

I'm unsure what your timing is.  Can you carry "mm: thp: Set the
accessed flag for old pages on access fault" until either the whole
patchset is ready to merge or until the sched-numa situation has been
cleared up?
I think DaveM may want this patch for sparc, so I'll keep it separate from
the ARM patches and have a go at reworking it when the sched-numa stuff has
settled down. Is that all in linux-next btw? If so, I can use that as a
starting point to dealing with the mess.

Cheers,

Will

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