This patch improves the performance of event alternative lookup by
replacing the previous linear search with a more efficient binary
search. This change reduces the time complexity for the search process
from O(n) to O(log(n)). A pre-sorted table of event values and their
corresponding indices has been introduced to expedite the search
process.
Signed-off-by: Kuan-Wei Chiu <visitor...@gmail.com>
---
arch/powerpc/perf/power6-pmu.c | 43 ++++++++++++++++++++--------------
1 file changed, 26 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/perf/power6-pmu.c b/arch/powerpc/perf/power6-pmu.c
index 5729b6e059de..b6030ea130eb 100644
--- a/arch/powerpc/perf/power6-pmu.c
+++ b/arch/powerpc/perf/power6-pmu.c
@@ -335,25 +335,34 @@ static const unsigned int event_alternatives[][MAX_ALT] =
{
{ 0x3000fe, 0x400056 }, /* PM_DATA_FROM_L3MISS */
};
-/*
- * This could be made more efficient with a binary search on
- * a presorted list, if necessary
- */
static int find_alternatives_list(u64 event)
{
- int i, j;
- unsigned int alt;
-
- for (i = 0; i < ARRAY_SIZE(event_alternatives); ++i) {
- if (event < event_alternatives[i][0])
- return -1;
- for (j = 0; j < MAX_ALT; ++j) {
- alt = event_alternatives[i][j];
- if (!alt || event < alt)
- break;
- if (event == alt)
- return i;
- }
+ const unsigned int presort_event_table[] = {
+ 0x0130e8, 0x080080, 0x080088, 0x10000a, 0x10000b, 0x10000d,
0x10000e,
+ 0x100010, 0x10001a, 0x100026, 0x100054, 0x100056, 0x1000f0,
0x1000f8,
+ 0x1000fc, 0x200008, 0x20000e, 0x200010, 0x200012, 0x200054,
0x2000f0,
+ 0x2000f2, 0x2000f4, 0x2000f5, 0x2000f6, 0x2000f8, 0x2000fc,
0x2000fe,
+ 0x2d0030, 0x30000a, 0x30000c, 0x300010, 0x300012, 0x30001a,
0x300056,
+ 0x3000f0, 0x3000f2, 0x3000f6, 0x3000f8, 0x3000fc, 0x3000fe,
0x400006,
+ 0x400007, 0x40000a, 0x40000e, 0x400010, 0x400018, 0x400056,
0x4000f0,
+ 0x4000f8, 0x600005};
+ const unsigned int event_index_table[] = {
+ 0, 1, 2, 3, 4, 1, 5, 6, 7, 8, 9, 10, 11, 12, 13, 12,
14,
+ 7, 15, 2, 9, 16, 3, 4, 0, 17, 10, 18, 19, 20, 1, 17, 15,
19,
+ 18, 2, 16, 21, 8, 0, 22, 13, 14, 11, 21, 5, 20, 22, 1, 6,
3};
+ int lo = 0;
+ int hi = ARRAY_SIZE(presort_event_table) - 1;
+
+ while (lo <= hi) {
+ int mid = lo + (hi - lo) / 2;
+ unsigned int alt = presort_event_table[mid];
+
+ if (alt < event)
+ lo = mid + 1;
+ else if (alt > event)
+ hi = mid - 1;
+ else
+ return event_index_table[mid];
}
return -1;
}
--
2.25.1
