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.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
---
include/linux/mm_types.h | 12 ++++++++----
1 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 9fc0291..23bd1e2 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -199,7 +199,8 @@ struct vm_region {
* 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. */
@@ -207,9 +208,6 @@ struct vm_area_struct {
/* 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;
/*
@@ -220,6 +218,12 @@ struct vm_area_struct {
*/
unsigned long free_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 prio tree, or
--
1.7.7.6
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