parisc: unwind - optimise linked-list searches for modules

Having many 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
on other architectures reduced the number of steps in the
search to barely more than 1.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Kyle McMartin <kyle@redhat.com>

diff --git a/arch/parisc/kernel/unwind.c b/arch/parisc/kernel/unwind.c
index d58eac1a8288af9c07ef776faa9b29d6b1890a2e..76ed62ed785b6f4be9c1a6e663101ff3daeb6aa7 100644 (file)
--- a/arch/parisc/kernel/unwind.c
+++ b/arch/parisc/kernel/unwind.c
@@ -80,8 +80,11 @@ find_unwind_entry(unsigned long addr)
                        if (addr >= table->start && 
                            addr <= table->end)
                                e = find_unwind_entry_in_table(table, addr);
-                       if (e)
+                       if (e) {
+                               /* Move-to-front to exploit common traces */
+                               list_move(&table->list, &unwind_tables);
                                break;
+                       }
                }
 
        return e;