commit b84f0bfead0da0334aeff90a291fd00a84881538
Author: Markus Stockhausen <markus.stockhausen@xxxxxxxxxxx>
Date: Sun Aug 10 09:39:12 2014 +0000
raid6 algorithms: show xor_syndrome() benchmarks on startup
The benchmark numbers of the gen_syndrome() functions are displayed in
the kernel log. Do the same for the xor_syndrome() functions. This
will help to analyze performance problems and give an rough estimate
how well the algorithm works. The choice of the fastest algorithm will
still depend on the gen_syndrome() performance.
With the start/stop page implementation the speed can vary a lot in real
life. E.g. a change of page 0 & page 15 on a stripe will be harder to
compute than the case where page 0 & page 1 are XOR candidates. To be not
to enthusiatic about the expected speeds we will run a worse case test
that simulates a change on the upper half of the stripe. So we do:
1) calculation of P/Q for the upper pages
2) continuation of Q for the lower (empty) pages
diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index f0b1aa3..dc1ec40 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -131,11 +131,12 @@ static inline const struct raid6_recov_calls *raid6_choose_recov(void)
static inline const struct raid6_calls *raid6_choose_gen(
void *(*const dptrs)[(65536/PAGE_SIZE)+2], const int disks)
{
- unsigned long perf, bestperf, j0, j1;
+ unsigned long perf, bestgenperf, bestxorperf, 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 (bestperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
+ for (bestgenperf = 0, bestxorperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
if (!best || (*algo)->prefer >= best->prefer) {
if ((*algo)->valid && !(*algo)->valid())
continue;
@@ -153,19 +154,46 @@ static inline const struct raid6_calls *raid6_choose_gen(
}
preempt_enable();
- if (perf > bestperf) {
- bestperf = perf;
+ if (perf > bestgenperf) {
+ bestgenperf = perf;
best = *algo;
}
- printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
+ printk("raid6: %-8s gen() %5ld MB/s\n", (*algo)->name,
(perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
+
+ if (!(*algo)->hasxor)
+ continue;
+
+ perf = 0;
+
+ 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;
+
+ printk("raid6: %-8s xor() %5ld MB/s\n", (*algo)->name,
+ (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2+1));
}
}
if (best) {
- printk("raid6: using algorithm %s (%ld MB/s)\n",
+ printk("raid6: using algorithm %s gen() %ld MB/s",
best->name,
- (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
+ (bestgenperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
+ if (best->hasxor)
+ printk(", xor() %ld MB/s, rmw enabled",
+ (bestxorperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2+1));
+ printk("\n");
raid6_call = *best;
} else
printk("raid6: Yikes! No algorithm found!\n");
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