Renumber the features linearly, so that feature number N is at
position N in the array. This allows for O(1) look-ups, as opposed
to O(N) before. This makes sensors_lookup_feature_nr() 2.4 times
faster in my real-world tests, resulting in a 6% performance boost
on average in the runtime part of "sensors".
---
lib/access.c | 8 ++------
lib/sysfs.c | 15 +++++++++++++++
2 files changed, 17 insertions(+), 6 deletions(-)
--- lm-sensors-3.orig/lib/sysfs.c 2007-09-02 16:17:16.000000000 +0200
+++ lm-sensors-3/lib/sysfs.c 2007-09-02 16:17:52.000000000 +0200
@@ -178,6 +178,21 @@ static int sensors_read_dynamic_chip(sen
}
}
+ /* Renumber the features linearly, so that feature number N is at
+ position N in the array. This allows for O(1) look-ups. */
+ for (i = 0; i < fnum; i++) {
+ int j, old;
+
+ old = dyn_features[i].data.number;
+ dyn_features[i].data.number = i;
+ for (j = i + 1;
+ j < fnum && dyn_features[j].data.mapping != SENSORS_NO_MAPPING;
+ j++) {
+ if (dyn_features[j].data.mapping == old)
+ dyn_features[j].data.mapping = i;
+ }
+ }
+
chip->feature = dyn_features;
exit_free:
--- lm-sensors-3.orig/lib/access.c 2007-09-02 16:17:16.000000000 +0200
+++ lm-sensors-3/lib/access.c 2007-09-02 16:17:52.000000000 +0200
@@ -92,15 +92,11 @@ sensors_for_all_config_chips(const senso
const sensors_chip_feature *sensors_lookup_feature_nr(const sensors_chip_name *chip,
int feature)
{
- int i, j;
- const sensors_chip_feature *features;
+ int i;
for (i = 0; i < sensors_proc_chips_count; i++)
if (sensors_match_chip(&sensors_proc_chips[i].chip, chip)) {
- features = sensors_proc_chips[i].feature;
- for (j = 0; features[j].data.name; j++)
- if (features[j].data.number == feature)
- return features + j;
+ return sensors_proc_chips[i].feature + feature;
}
return NULL;
}
--
Jean Delvare
