ioremap uses __get_vm_area_node which sets alignment to fls of requested size.
I couldn't find any reason for such big align. Does it decrease TLB misses?
I tested it on custom ARM board with 200+ Mb of ioremap and it works.
What am I missing?
Alignment restriction for ioremap region was introduced with the commit:
> Author: James Bottomley <jejb@mulgrave.(none)>
> Date: Wed Jun 30 11:11:14 2004 -0500
>
> Add vmalloc alignment constraints
>
> vmalloc is used by ioremap() to get regions for
> remapping I/O space. To feed these regions back
> into a __get_free_pages() type memory allocator,
> they are expected to have more alignment than
> get_vm_area() proves. So add additional alignment
> constraints for VM_IOREMAP.
>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: Guan Xuetao <gxt@xxxxxxxxxxxxxxx>
Cc: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>
Cc: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Arnd Bergmann <arnd.bergmann@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dyasly Sergey <s.dyasly@xxxxxxxxxxx>
Signed-off-by: Dmitry Safonov <d.safonov@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/include/asm/memory.h | 5 -----
arch/unicore32/include/asm/memory.h | 5 -----
include/linux/vmalloc.h | 8 --------
mm/vmalloc.c | 2 --
4 files changed, 20 deletions(-)
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 184def0..b333245 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -78,11 +78,6 @@
*/
#define XIP_VIRT_ADDR(physaddr) (MODULES_VADDR + ((physaddr) & 0x000fffff))
-/*
- * Allow 16MB-aligned ioremap pages
- */
-#define IOREMAP_MAX_ORDER 24
-
#else /* CONFIG_MMU */
/*
diff --git a/arch/unicore32/include/asm/memory.h b/arch/unicore32/include/asm/memory.h
index debafc4..ffae189 100644
--- a/arch/unicore32/include/asm/memory.h
+++ b/arch/unicore32/include/asm/memory.h
@@ -46,11 +46,6 @@
#define MODULES_END (PAGE_OFFSET)
/*
- * Allow 16MB-aligned ioremap pages
- */
-#define IOREMAP_MAX_ORDER 24
-
-/*
* Physical vs virtual RAM address space conversion. These are
* private definitions which should NOT be used outside memory.h
* files. Use virt_to_phys/phys_to_virt/__pa/__va instead.
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index b87696f..2f428e8 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -18,14 +18,6 @@ struct vm_area_struct; /* vma defining user mapping in mm_types.h */
#define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
/* bits [20..32] reserved for arch specific ioremap internals */
-/*
- * Maximum alignment for ioremap() regions.
- * Can be overriden by arch-specific value.
- */
-#ifndef IOREMAP_MAX_ORDER
-#define IOREMAP_MAX_ORDER (7 + PAGE_SHIFT) /* 128 pages */
-#endif
-
struct vm_struct {
struct vm_struct *next;
void *addr;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 39c3388..c4f480dd 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1313,8 +1313,6 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
struct vm_struct *area;
BUG_ON(in_interrupt());
- if (flags & VM_IOREMAP)
- align = 1ul << clamp(fls(size), PAGE_SHIFT, IOREMAP_MAX_ORDER);
size = PAGE_ALIGN(size);
if (unlikely(!size))
--
1.9.1
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