Exception handlers are aligned to 128 bytes (L1 cache) on 64s, which is
overkill. It can reduce the icache footprint of any individual exception
path. However taken as a whole, the expansion in icache footprint seems
likely to be counter-productive and cause more total misses.
Create IFETCH_ALIGN_SHIFT/BYTES, which should give optimal ifetch
alignment with much more reasonable alignment. This saves 1792 bytes
from head_64.o text with an allmodconfig build.
Other subarchitectures should define appropriate IFETCH_ALIGN_SHIFT
values if this becomes more widely used.
Cc: Anton Blanchard <an...@samba.org>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/include/asm/cache.h | 3 +++
arch/powerpc/include/asm/head-64.h | 8 ++++----
arch/powerpc/kernel/exceptions-64s.S | 2 +-
3 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/cache.h b/arch/powerpc/include/asm/cache.h
index ffbafbf..7657aa8 100644
--- a/arch/powerpc/include/asm/cache.h
+++ b/arch/powerpc/include/asm/cache.h
@@ -20,12 +20,15 @@
#endif
#else /* CONFIG_PPC64 */
#define L1_CACHE_SHIFT 7
+#define IFETCH_ALIGN_SHIFT 4 /* POWER8,9 */
#endif
#define L1_CACHE_BYTES (1 << L1_CACHE_SHIFT)
#define SMP_CACHE_BYTES L1_CACHE_BYTES
+#define IFETCH_ALIGN_BYTES (1 << IFETCH_ALIGN_SHIFT)
+
#if defined(__powerpc64__) && !defined(__ASSEMBLY__)
struct ppc64_caches {
u32 dsize; /* L1 d-cache size */
diff --git a/arch/powerpc/include/asm/head-64.h
b/arch/powerpc/include/asm/head-64.h
index ab90c2f..fca7033 100644
--- a/arch/powerpc/include/asm/head-64.h
+++ b/arch/powerpc/include/asm/head-64.h
@@ -95,12 +95,12 @@ end_##sname:
#define __FIXED_SECTION_ENTRY_BEGIN(sname, name, __align) \
USE_FIXED_SECTION(sname); \
- .align __align; \
+ .balign __align; \
.global name; \
name:
#define FIXED_SECTION_ENTRY_BEGIN(sname, name) \
- __FIXED_SECTION_ENTRY_BEGIN(sname, name, 0)
+ __FIXED_SECTION_ENTRY_BEGIN(sname, name, IFETCH_ALIGN_BYTES)
#define FIXED_SECTION_ENTRY_BEGIN_LOCATION(sname, name, start) \
USE_FIXED_SECTION(sname); \
@@ -203,9 +203,9 @@ end_##sname:
#define EXC_VIRT_END(name, start, end) \
FIXED_SECTION_ENTRY_END_LOCATION(virt_vectors,
exc_virt_##start##_##name, end)
-#define EXC_COMMON_BEGIN(name) \
+#define EXC_COMMON_BEGIN(name) \
USE_TEXT_SECTION(); \
- .align 7; \
+ .balign IFETCH_ALIGN_BYTES; \
.global name; \
DEFINE_FIXED_SYMBOL(name); \
name:
diff --git a/arch/powerpc/kernel/exceptions-64s.S
b/arch/powerpc/kernel/exceptions-64s.S
index e680e84..4af87e4 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1403,7 +1403,7 @@ USE_TEXT_SECTION()
/*
* Hash table stuff
*/
- .align 7
+ .balign IFETCH_ALIGN_BYTES
do_hash_page:
#ifdef CONFIG_PPC_STD_MMU_64
andis. r0,r4,0xa410 /* weird error? */
--
2.9.3
