ARM: 6341/1: unwind - optimise linked-list searches for modules

With several sections per module, and dozens of modules, the
searches down the linked list of sections would dominate the
lookup time, dwarfing any savings from the binary search
within the section.

A simple move-to-front optimisation exploits the commonality
of the code paths taken, and in simple real-world tests reduces
the number of steps in the search to barely more than 1.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index dd81a91..2a16176 100644 (file)
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -146,6 +146,8 @@ static struct unwind_idx *unwind_find_idx(unsigned long addr)
                            addr < table->end_addr) {
                                idx = search_index(addr, table->start,
                                                   table->stop - 1);
+                               /* Move-to-front to exploit common traces */
+                               list_move(&table->list, &unwind_tables);
                                break;
                        }
                }