[PATCH 04/16] mm: rearrange vm_area_struct for fewer cache misses
From: Michel Lespinasse <hidden>
Date: 2012-11-05 22:52:04
Also in:
linux-mips, linux-mm, linux-sh, lkml, sparclinux
Subsystem:
memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
From: Rik van Riel <riel@surriel.com> 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: Michel Lespinasse <redacted> Signed-off-by: Rik van Riel <redacted> --- 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 94fa52b28ee8..528da4abf8ee 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h@@ -224,7 +224,8 @@ 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. */
@@ -232,9 +233,6 @@ 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; /*
@@ -245,6 +243,12 @@ struct vm_area_struct { */ 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
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