Commit 38640c48 authored by Dirk Müller's avatar Dirk Müller Committed by Song Liu
Browse files

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



In commit fe5cbc6e ("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: default avatarDirk Müller <dmueller@suse.de>
Signed-off-by: default avatarSong Liu <song@kernel.org>
parent dd3dc5f4

lib/raid6/algos.c

+37 −39
Original line number Diff line number Diff line
@@ -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;
@@ -180,10 +180,28 @@ 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;

	}



	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;



		preempt_disable();
@@ -192,38 +210,18 @@ static inline const struct raid6_calls *raid6_choose_gen( 
			cpu_relax();

		while (time_before(jiffies,

				   j1 + (1 << RAID6_TIME_JIFFIES_LG2))) {

				(*algo)->xor_syndrome(disks, start, stop,

			best->xor_syndrome(disks, start, stop,

					   PAGE_SIZE, *dptrs);

			perf++;

		}

		preempt_enable();



			if (best == *algo)

				bestxorperf = perf;



			pr_info("raid6: %-8s xor() %5ld MB/s\n", (*algo)->name,

		pr_info("raid6: .... xor() %ld MB/s, rmw enabled\n",

			(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",

					(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");



out:

	return best;

}