hollalinux
/
linux-sg2042
mirror of https://github.com/sophgo/linux-riscv.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

powerpc/64s: Reduce exception alignment 

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.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2016-10-13 14:43:52 +11:00 committed by Michael Ellerman
parent fda0440d82
commit f4329f2ecb
3 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/powerpc/include/asm/cache.h
View File

@ -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 */

8
arch/powerpc/include/asm/head-64.h
View File

@ -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 @@ name:
#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:

2
arch/powerpc/kernel/exceptions-64s.S
View File

@ -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? */