diff options
| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2012-11-08 14:18:47 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2012-11-13 11:03:09 +0100 |
| commit | 4bffbb3455372a26816e364fb4448810f7014452 (patch) | |
| tree | af64b28c6bd246a9078edb624fad787e3b4fc1f2 /arch | |
| parent | 516bad44b9f3bdcb0be6be0252b7557bf7a149e4 (diff) | |
s390/mm: have 16 byte aligned struct pages
Select HAVE_ALIGNED_STRUCT_PAGE on s390, so that the slub allocator can make
use of compare and swap double for lockless updates. This increases the size
of struct page to 64 bytes (instead of 56 bytes), however the performance gain
justifies the increased size:
- now excactly four struct pages fit into a single cache line; the
case that accessing a struct page causes two cache line loads
does not exist anymore.
- calculating the offset of a struct page within the memmap array
is only a simple shift instead of a more expensive multiplication.
A "hackbench 200 process 200" run on a 32 cpu system did show an 8% runtime
improvement.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 5dba755a43e6..d385f396dfee 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -96,6 +96,7 @@ config S390 select HAVE_MEMBLOCK_NODE_MAP select HAVE_CMPXCHG_LOCAL select HAVE_CMPXCHG_DOUBLE + select HAVE_ALIGNED_STRUCT_PAGE if SLUB select HAVE_VIRT_CPU_ACCOUNTING select VIRT_CPU_ACCOUNTING select ARCH_DISCARD_MEMBLOCK |