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lib/raid6: skip benchmark of non-chosen xor_syndrome functions

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In commit fe5cbc6e06 ("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@suse.de>
Signed-off-by: Song Liu <song@kernel.org>
This commit is contained in:
Dirk Müller 2022-01-05 17:38:46 +01:00 • committed by Song Liu
parent dd3dc5f416
commit 38640c4809
1 changed files with 40 additions and 42 deletions
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56
lib/raid6/algos.c
View file

@ -145,12 +145,12 @@ static inline const struct raid6_recov_calls *raid6_choose_recov(void)
static inline const struct raid6_calls *raid6_choose_gen( static inline const struct raid6_calls *raid6_choose_gen(
void *(*const dptrs)[RAID6_TEST_DISKS], const int disks) 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 */ 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 *const *algo;
const struct raid6_calls *best; 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 (!best || (*algo)->prefer >= best->prefer) {
if ((*algo)->valid && !(*algo)->valid()) if ((*algo)->valid && !(*algo)->valid())
continue; continue;
@ -180,10 +180,28 @@ static inline const struct raid6_calls *raid6_choose_gen(
pr_info("raid6: %-8s gen() %5ld MB/s\n", (*algo)->name, pr_info("raid6: %-8s gen() %5ld MB/s\n", (*algo)->name,
(perf * HZ * (disks-2)) >> (perf * HZ * (disks-2)) >>
(20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2)); (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2));
}
}
if (!(*algo)->xor_syndrome) if (!best) {
continue; pr_err("raid6: Yikes! No algorithm found!\n");
goto out;
}
raid6_call = *best;
if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
pr_info("raid6: skipped pq benchmark and selected %s\n",
best->name);
goto out;
}
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; perf = 0;
preempt_disable(); preempt_disable();
@ -191,39 +209,19 @@ static inline const struct raid6_calls *raid6_choose_gen(
while ((j1 = jiffies) == j0) while ((j1 = jiffies) == j0)
cpu_relax(); cpu_relax();
while (time_before(jiffies, while (time_before(jiffies,
j1 + (1<<RAID6_TIME_JIFFIES_LG2))) { j1 + (1 << RAID6_TIME_JIFFIES_LG2))) {
(*algo)->xor_syndrome(disks, start, stop, best->xor_syndrome(disks, start, stop,
PAGE_SIZE, *dptrs); PAGE_SIZE, *dptrs);
perf++; perf++;
} }
preempt_enable(); preempt_enable();
if (best == *algo)
bestxorperf = perf;
pr_info("raid6: %-8s xor() %5ld MB/s\n", (*algo)->name,
(perf * HZ * (disks-2)) >>
(20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2 + 1));
}
}
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", pr_info("raid6: .... xor() %ld MB/s, rmw enabled\n",
(bestxorperf * HZ * (disks-2)) >> (perf * HZ * (disks - 2)) >>
(20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2 + 1)); (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");
out:
return best; return best;
} }