lkml.org 
[lkml]   [2012]   [Oct]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 16/31] numa, mm: Support NUMA hinting page faults from gup/gup_fast
From: Ingo Molnar <mingo@kernel.org>

Introduce FOLL_NUMA to tell follow_page to check
pte/pmd_numa. get_user_pages must use FOLL_NUMA, and it's safe to do
so because it always invokes handle_mm_fault and retries the
follow_page later.

KVM secondary MMU page faults will trigger the NUMA hinting page
faults through gup_fast -> get_user_pages -> follow_page ->
handle_mm_fault.

Other follow_page callers like KSM should not use FOLL_NUMA, or they
would fail to get the pages if they use follow_page instead of
get_user_pages.

[ This patch was picked up from the AutoNUMA tree. ]

Originally-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
[ ported to this tree. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/mm.h | 1 +
mm/memory.c | 17 +++++++++++++++++
2 files changed, 18 insertions(+)

Index: tip/include/linux/mm.h
===================================================================
--- tip.orig/include/linux/mm.h
+++ tip/include/linux/mm.h
@@ -1600,6 +1600,7 @@ struct page *follow_page(struct vm_area_
#define FOLL_MLOCK 0x40 /* mark page as mlocked */
#define FOLL_SPLIT 0x80 /* don't return transhuge pages, split them */
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
+#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */

typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
void *data);
Index: tip/mm/memory.c
===================================================================
--- tip.orig/mm/memory.c
+++ tip/mm/memory.c
@@ -1536,6 +1536,8 @@ struct page *follow_page(struct vm_area_
page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
goto out;
}
+ if ((flags & FOLL_NUMA) && pmd_numa(vma, *pmd))
+ goto no_page_table;
if (pmd_trans_huge(*pmd)) {
if (flags & FOLL_SPLIT) {
split_huge_page_pmd(mm, pmd);
@@ -1565,6 +1567,8 @@ split_fallthrough:
pte = *ptep;
if (!pte_present(pte))
goto no_page;
+ if ((flags & FOLL_NUMA) && pte_numa(vma, pte))
+ goto no_page;
if ((flags & FOLL_WRITE) && !pte_write(pte))
goto unlock;

@@ -1716,6 +1720,19 @@ int __get_user_pages(struct task_struct
(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
vm_flags &= (gup_flags & FOLL_FORCE) ?
(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
+
+ /*
+ * If FOLL_FORCE and FOLL_NUMA are both set, handle_mm_fault
+ * would be called on PROT_NONE ranges. We must never invoke
+ * handle_mm_fault on PROT_NONE ranges or the NUMA hinting
+ * page faults would unprotect the PROT_NONE ranges if
+ * _PAGE_NUMA and _PAGE_PROTNONE are sharing the same pte/pmd
+ * bitflag. So to avoid that, don't set FOLL_NUMA if
+ * FOLL_FORCE is set.
+ */
+ if (!(gup_flags & FOLL_FORCE))
+ gup_flags |= FOLL_NUMA;
+
i = 0;

do {



\
 
 \ /
  Last update: 2012-10-25 16:01    [W:0.298 / U:0.180 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site