In commit fe5cbc6e06c7 ("md/raid6 algorithms: delta syndrome functions")
a xor_syndrome() benchmarking was added also to the raid6_choose_gen()
function. However, the results of that benchmarking were intentionally
discarded and did not influence the choice. It picked the
xor_syndrome() variant related to the best performing gen_syndrome().
Reduce runtime of raid6_choose_gen() without modifying its outcome by
only benchmarking the xor_syndrome() of the best gen_syndrome() variant.
For a HZ=250 x86_64 system with avx2 and without avx512 this removes
5 out of 6 xor() benchmarks, saving 340ms of raid6 initialization time.
Signed-off-by: Dirk Müller <dmueller@xxxxxxx>
---
lib/raid6/algos.c | 76 +++++++++++++++++++++++------------------------
1 file changed, 37 insertions(+), 39 deletions(-)
diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index 6d5e5000fdd7..9b7e8a837b27 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -145,12 +145,12 @@ static inline const struct raid6_recov_calls *raid6_choose_recov(void)
static inline const struct raid6_calls *raid6_choose_gen(
void *(*const dptrs)[RAID6_TEST_DISKS], const int disks)
{
- unsigned long perf, bestgenperf, bestxorperf, j0, j1;
+ unsigned long perf, bestgenperf, j0, j1;
int start = (disks>>1)-1, stop = disks-3; /* work on the second half of the disks */
const struct raid6_calls *const *algo;
const struct raid6_calls *best;
- for (bestgenperf = 0, bestxorperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
+ for (bestgenperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
if (!best || (*algo)->prefer >= best->prefer) {
if ((*algo)->valid && !(*algo)->valid())
continue;
@@ -180,50 +180,48 @@ static inline const struct raid6_calls *raid6_choose_gen(
pr_info("raid6: %-8s gen() %5ld MB/s\n", (*algo)->name,
(perf * HZ * (disks-2)) >>
(20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2));
+ }
+ }
- if (!(*algo)->xor_syndrome)
- continue;
+ if (!best) {
+ pr_err("raid6: Yikes! No algorithm found!\n");
+ goto out;
+ }
- perf = 0;
+ raid6_call = *best;
- preempt_disable();
- j0 = jiffies;
- while ((j1 = jiffies) == j0)
- cpu_relax();
- while (time_before(jiffies,
- j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
- (*algo)->xor_syndrome(disks, start, stop,
- PAGE_SIZE, *dptrs);
- perf++;
- }
- preempt_enable();
-
- if (best == *algo)
- bestxorperf = perf;
+ if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
+ pr_info("raid6: skipped pq benchmark and selected %s\n",
+ best->name);
+ goto out;
+ }
- pr_info("raid6: %-8s xor() %5ld MB/s\n", (*algo)->name,
- (perf * HZ * (disks-2)) >>
- (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2 + 1));
+ pr_info("raid6: using algorithm %s gen() %ld MB/s\n",
+ best->name,
+ (bestgenperf * HZ * (disks - 2)) >>
+ (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2));
+
+ if (best->xor_syndrome) {
+ perf = 0;
+
+ preempt_disable();
+ j0 = jiffies;
+ while ((j1 = jiffies) == j0)
+ cpu_relax();
+ while (time_before(jiffies,
+ j1 + (1 << RAID6_TIME_JIFFIES_LG2))) {
+ best->xor_syndrome(disks, start, stop,
+ PAGE_SIZE, *dptrs);
+ perf++;
}
- }
+ preempt_enable();
- if (best) {
- if (IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
- pr_info("raid6: using algorithm %s gen() %ld MB/s\n",
- best->name,
- (bestgenperf * HZ * (disks-2)) >>
- (20 - PAGE_SHIFT+RAID6_TIME_JIFFIES_LG2));
- if (best->xor_syndrome)
- pr_info("raid6: .... xor() %ld MB/s, rmw enabled\n",
- (bestxorperf * HZ * (disks-2)) >>
- (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2 + 1));
- } else
- pr_info("raid6: skip pq benchmark and using algorithm %s\n",
- best->name);
- raid6_call = *best;
- } else
- pr_err("raid6: Yikes! No algorithm found!\n");
+ pr_info("raid6: .... xor() %ld MB/s, rmw enabled\n",
+ (perf * HZ * (disks - 2)) >>
+ (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2 + 1));
+ }
+out:
return best;
}
--
2.34.1
