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: Andrew Morton <akpm@linux-foundation.org>
Date: 2012-10-23 21:50:30
Also in: linux-mm, lkml

On Tue, 23 Oct 2012 11:11:25 +0100
Will Deacon [off-list ref] wrote:
On Mon, Oct 22, 2012 at 07:18:43PM +0100, Andrew Morton wrote:
quoted
On Mon, 22 Oct 2012 11:35:03 +0100
Will Deacon [off-list ref] wrote:
quoted
On Fri, Oct 19, 2012 at 07:49:55PM +0100, Andrew Morton wrote:
quoted
Ho hum.  I'll drop
mm-thp-set-the-accessed-flag-for-old-pages-on-access-fault.patch and
shall assume that you'll sort things out at the appropriate time.
Happy to sort it out once I work out what's going wrong!
The patch "ARM: mm: Transparent huge page support for LPAE systems" is
not present in linux-next, so this patch ("mm: thp: Set the accessed
flag for old pages on access fault") will not compile?
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?
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