x86: add missed pgtable_pmd_page_ctor/dtor calls for preallocated pmds

In split page table lock case, we embed spinlock_t into struct page.
For obvious reason, we don't want to increase size of struct page if
spinlock_t is too big, like with DEBUG_SPINLOCK or DEBUG_LOCK_ALLOC or
on -rt kernel.  So we disable split page table lock, if spinlock_t is
too big.

This patchset allows to allocate the lock dynamically if spinlock_t is
big.  In this page->ptl is used to store pointer to spinlock instead of
spinlock itself.  It costs additional cache line for indirect access,
but fix page fault scalability for multi-threaded applications.

LOCK_STAT depends on DEBUG_SPINLOCK, so on current kernel enabling
LOCK_STAT to analyse scalability issues breaks scalability.  ;)

The patchset mostly fixes this.  Results for ./thp_memscale -c 80 -b 512M
on 4-socket machine:

baseline, no CONFIG_LOCK_STAT:	9.115460703 seconds time elapsed
baseline, CONFIG_LOCK_STAT=y:	53.890567123 seconds time elapsed
patched, no CONFIG_LOCK_STAT:	8.852250368 seconds time elapsed
patched, CONFIG_LOCK_STAT=y:	11.069770759 seconds time elapsed

Patch count is scary, but most of them trivial. Overview:

 Patches 1-4	Few bug fixes. No dependencies to other patches.
		Probably should applied as soon as possible.

 Patch 5	Changes signature of pgtable_page_ctor(). We will use it
		for dynamic lock allocation, so it can fail.

 Patches 6-8	Add missing constructor/destructor calls on few archs.
		It's fixes NR_PAGETABLE accounting and prepare to use
		split ptl.

 Patches 9-33	Add pgtable_page_ctor() fail handling to all archs.

 Patches 34	Finally adds support of dynamically-allocated page->pte.
		Also contains documentation for split page table lock.

This patch (of 34):

I've missed that we preallocate few pmds on pgd_alloc() if X86_PAE
enabled.  Let's add missed constructor/destructor calls.

I haven't noticed it during testing since prep_new_page() clears
page->mapping and therefore page->ptl.  It's effectively equal to
spin_lock_init(&page->ptl).

Signed-off-by: Kirill A. Shutemov <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chen Liqin <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Howells <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Grant Likely <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Haavard Skinnemoen <[email protected]>
Cc: Hans-Christian Egtvedt <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Hirokazu Takata <[email protected]>
Cc: Ivan Kokshaysky <[email protected]>
Cc: James Hogan <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Jesper Nilsson <[email protected]>
Cc: Jonas Bonn <[email protected]>
Cc: Koichi Yasutake <[email protected]>
Cc: Lennox Wu <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Mikael Starvik <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Richard Kuo <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Russell King <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 9 insertions, 2 deletions

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index dfa537a03be1..1a7d21342e02 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -189,8 +189,10 @@ static void free_pmds(pmd_t *pmds[])
 	int i;
 
 	for(i = 0; i < PREALLOCATED_PMDS; i++)
-		if (pmds[i])
+		if (pmds[i]) {
+			pgtable_pmd_page_dtor(virt_to_page(pmds[i]));
 			free_page((unsigned long)pmds[i]);
+		}
 }
 
 static int preallocate_pmds(pmd_t *pmds[])
@@ -200,8 +202,13 @@ static int preallocate_pmds(pmd_t *pmds[])
 
 	for(i = 0; i < PREALLOCATED_PMDS; i++) {
 		pmd_t *pmd = (pmd_t *)__get_free_page(PGALLOC_GFP);
-		if (pmd == NULL)
+		if (!pmd)
+			failed = true;
+		if (pmd && !pgtable_pmd_page_ctor(virt_to_page(pmd))) {
+			free_page((unsigned long)pmds[i]);
+			pmd = NULL;
 			failed = true;
+		}
 		pmds[i] = pmd;
 	}