mm: rearrange vm_area_struct for fewer cache misses
The kernel walks the VMA rbtree in various places, including the page
fault path. However, the vm_rb node spanned two cache lines, on 64 bit
systems with 64 byte cache lines (most x86 systems).
Rearrange vm_area_struct a little, so all the information we need to do a
VMA tree walk is in the first cache line.
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 94fa52b..7ade273 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -224,7 +224,8 @@
* library, the executable area etc).
*/
struct vm_area_struct {
- struct mm_struct * vm_mm; /* The address space we belong to. */
+ /* The first cache line has the info for VMA tree walking. */
+
unsigned long vm_start; /* Our start address within vm_mm. */
unsigned long vm_end; /* The first byte after our end address
within vm_mm. */
@@ -232,9 +233,6 @@
/* linked list of VM areas per task, sorted by address */
struct vm_area_struct *vm_next, *vm_prev;
- pgprot_t vm_page_prot; /* Access permissions of this VMA. */
- unsigned long vm_flags; /* Flags, see mm.h. */
-
struct rb_node vm_rb;
/*
@@ -245,6 +243,12 @@
*/
unsigned long rb_subtree_gap;
+ /* Second cache line starts here. */
+
+ struct mm_struct *vm_mm; /* The address space we belong to. */
+ pgprot_t vm_page_prot; /* Access permissions of this VMA. */
+ unsigned long vm_flags; /* Flags, see mm.h. */
+
/*
* For areas with an address space and backing store,
* linkage into the address_space->i_mmap interval tree, or