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authorChen, Kenneth W <kenneth.w.chen@intel.com>2006-10-13 10:08:13 -0700
committerTony Luck <tony.luck@intel.com>2007-02-06 15:04:48 -0800
commit00b65985fb2fc542b855b03fcda0d0f2bab4f442 (patch)
treedc9372aced10184945862b9adf0848da3e0e946f /include/asm-ia64/kregs.h
parenta0776ec8e97bf109e7d973d09fc3e1814eb32bfb (diff)
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[IA64] relax per-cpu TLB requirement to DTC
Instead of pinning per-cpu TLB into a DTR, use DTC. This will free up one TLB entry for application, or even kernel if access pattern to per-cpu data area has high temporal locality. Since per-cpu is mapped at the top of region 7 address, we just need to add special case in alt_dtlb_miss. The physical address of per-cpu data is already conveniently stored in IA64_KR(PER_CPU_DATA). Latency for alt_dtlb_miss is not affected as we can hide all the latency. It was measured that alt_dtlb_miss handler has 23 cycles latency before and after the patch. The performance effect is massive for applications that put lots of tlb pressure on CPU. Workload environment like database online transaction processing or application uses tera-byte of memory would benefit the most. Measurement with industry standard database benchmark shown an upward of 1.6% gain. While smaller workloads like cpu, java also showing small improvement. Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'include/asm-ia64/kregs.h')
-rw-r--r--include/asm-ia64/kregs.h3
1 files changed, 1 insertions, 2 deletions
diff --git a/include/asm-ia64/kregs.h b/include/asm-ia64/kregs.h
index 221b5cb..7e55a58 100644
--- a/include/asm-ia64/kregs.h
+++ b/include/asm-ia64/kregs.h
@@ -29,8 +29,7 @@
*/
#define IA64_TR_KERNEL 0 /* itr0, dtr0: maps kernel image (code & data) */
#define IA64_TR_PALCODE 1 /* itr1: maps PALcode as required by EFI */
-#define IA64_TR_PERCPU_DATA 1 /* dtr1: percpu data */
-#define IA64_TR_CURRENT_STACK 2 /* dtr2: maps kernel's memory- & register-stacks */
+#define IA64_TR_CURRENT_STACK 1 /* dtr1: maps kernel's memory- & register-stacks */
/* Processor status register bits: */
#define IA64_PSR_BE_BIT 1