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authorPhil Carmody <ext-phil.2.carmody@nokia.com>2010-09-14 16:35:39 -0400
committerTony Luck <tony.luck@intel.com>2010-09-14 16:35:39 -0400
commit04a344069052d94b4ea1f95d930cbfa39b4ca292 (patch)
tree1caa4caa3d023435819c6dc5ed6f90701a8c97e1 /arch/ia64/kernel
parent747584be04bb98a856bab5cd1bfe56d341881b83 (diff)
[IA64] unwind - optimise linked-list searches for modules
It's clear from the comment in the code about keeping the kernel's unwind table at the front of the list that some attention has been paid to access patterns. Tests on other architectures have shown that a move-to-front optimisation improves searches dramatically. Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'arch/ia64/kernel')
-rw-r--r--arch/ia64/kernel/unwind.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/arch/ia64/kernel/unwind.c b/arch/ia64/kernel/unwind.c
index f47217b1bb37..fed6afa2e8a9 100644
--- a/arch/ia64/kernel/unwind.c
+++ b/arch/ia64/kernel/unwind.c
@@ -1531,7 +1531,7 @@ build_script (struct unw_frame_info *info)
1531 struct unw_labeled_state *ls, *next; 1531 struct unw_labeled_state *ls, *next;
1532 unsigned long ip = info->ip; 1532 unsigned long ip = info->ip;
1533 struct unw_state_record sr; 1533 struct unw_state_record sr;
1534 struct unw_table *table; 1534 struct unw_table *table, *prev;
1535 struct unw_reg_info *r; 1535 struct unw_reg_info *r;
1536 struct unw_insn insn; 1536 struct unw_insn insn;
1537 u8 *dp, *desc_end; 1537 u8 *dp, *desc_end;
@@ -1560,11 +1560,26 @@ build_script (struct unw_frame_info *info)
1560 1560
1561 STAT(parse_start = ia64_get_itc()); 1561 STAT(parse_start = ia64_get_itc());
1562 1562
1563 prev = NULL;
1563 for (table = unw.tables; table; table = table->next) { 1564 for (table = unw.tables; table; table = table->next) {
1564 if (ip >= table->start && ip < table->end) { 1565 if (ip >= table->start && ip < table->end) {
1566 /*
1567 * Leave the kernel unwind table at the very front,
1568 * lest moving it breaks some assumption elsewhere.
1569 * Otherwise, move the matching table to the second
1570 * position in the list so that traversals can benefit
1571 * from commonality in backtrace paths.
1572 */
1573 if (prev && prev != unw.tables) {
1574 /* unw is safe - we're already spinlocked */
1575 prev->next = table->next;
1576 table->next = unw.tables->next;
1577 unw.tables->next = table;
1578 }
1565 e = lookup(table, ip - table->segment_base); 1579 e = lookup(table, ip - table->segment_base);
1566 break; 1580 break;
1567 } 1581 }
1582 prev = table;
1568 } 1583 }
1569 if (!e) { 1584 if (!e) {
1570 /* no info, return default unwinder (leaf proc, no mem stack, no saved regs) */ 1585 /* no info, return default unwinder (leaf proc, no mem stack, no saved regs) */