From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE4093B27F4; Wed, 15 Jul 2026 14:48:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784126935; cv=none; b=Sd3rU+Fxf9CqsDaqHZLS0ShZBTtfZ1l+Gkft0xAKPareu/8/b3mvoah+3mTEdUGUh610dbht1Ueb34dme8oi3kp2idNm8Qr6CuyQj5ZZR0zZOlob1EMIfSVztiHlOMN473L0W/zvQEOiKOaF1GE2WTUWFfAlwioUBnEYkKS+3GU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784126935; c=relaxed/simple; bh=uvLbQuLQegueOfQ3Ywx/Qx3bk2Ygv/4XBp4Ey1kbEM4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Qbq0V4UzU6OSzGrVQK9Pa0HSIQGTirid3HbhE2+s4yF2t7TmVsD8DOHsGu625ifvp8AEXS9ajxNfixYzcCxeG/P5jj7E1uC2LvVwoNDJQ+BLCN0TySo6ONYJ3MIGK+KDjXSUyhR0vACKMmso91KPPSBlMKtBGxVF3W00y2WbtDE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=lst.de; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=3gdvIbjw; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="3gdvIbjw" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=6dCRrdTw19wsbl5ZzjUchkYHI2TZvOISnptCJJ38J0U=; b=3gdvIbjw1Jf4vxkOlNkdSmgDOQ xIZ9ONb1ZjrL/tQ3QUX2i/r7eFEkhzpAC+JjqPMMgbYhkhcZVjfUgu2AushGj7vT0CNt6h+nChARM xYDvWfPevveLMqqBHz78O1eln1vwdPahvxsJ5sUG8YGtT1dkE0fE6viyfsSdPSksJdkOW+y1NWtHK KGPw7WAVMRQq2suYPFPIOAlld/SKb6SRZ480UEY3Tu+jbcuaLY/ehdzuQq88ZjBNMKYUc/sRuR/T9 ibcXQfTiDHzTceKp0shfpgbDWa6NoTxPBpYOWQr7fH9y8VyBrf5yn1vwFGvDx1PcDfYlhEKb0Sd4M wwTfsw7w==; Received: from 2a02-8389-2301-9f00-b29a-36e9-8c1c-0994.cable.dynamic.v6.surfer.at ([2a02:8389:2301:9f00:b29a:36e9:8c1c:994] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wk0uq-0000000FDBv-3Z5A; Wed, 15 Jul 2026 14:48:53 +0000 From: Christoph Hellwig To: Andrew Morton Cc: Eric Biggers , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 7/8] raid6: improve the runtime selection benchmark Date: Wed, 15 Jul 2026 16:47:38 +0200 Message-ID: <20260715144825.95432-8-hch@lst.de> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260715144825.95432-1-hch@lst.de> References: <20260715144825.95432-1-hch@lst.de> Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Use plain ktime_get_ns for the timing, use 8 + 2 disks for a realistic load, and report the throughput on the data disks as that is what storage systems are measured on. Signed-off-by: Christoph Hellwig --- lib/raid/raid6/algos.c | 77 +++++++++++++++++++----------------------- 1 file changed, 35 insertions(+), 42 deletions(-) diff --git a/lib/raid/raid6/algos.c b/lib/raid/raid6/algos.c index 702e167a543a..011aa9d0eb3c 100644 --- a/lib/raid/raid6/algos.c +++ b/lib/raid/raid6/algos.c @@ -152,40 +152,37 @@ void raid6_recov_datap(int disks, size_t bytes, int faila, void **ptrs) } EXPORT_SYMBOL_GPL(raid6_recov_datap); -#define RAID6_TIME_JIFFIES_LG2 4 -#define RAID6_TEST_DISKS 8 +#define BENCH_SIZE SZ_4K +#define NR_SRCS 8 +#define NR_DISKS (NR_SRCS + 2) +#define REPS 800U -static int raid6_choose_gen(void *(*const dptrs)[RAID6_TEST_DISKS], - const int disks) +static int raid6_choose_gen(void *dptrs[NR_DISKS], const int disks) { - /* work on the second half of the disks */ - int start = (disks >> 1) - 1, stop = disks - 3; const struct raid6_calls *best = NULL; unsigned long bestgenperf = 0; unsigned int i; for (i = 0; i < raid6_nr_algos; i++) { const struct raid6_calls *algo = raid6_algos[i]; - unsigned long perf = 0, j0, j1; + unsigned long perf = 0; + u64 t; + int i; preempt_disable(); - j0 = jiffies; - while ((j1 = jiffies) == j0) - cpu_relax(); - while (time_before(jiffies, - j1 + (1<gen_syndrome(disks, PAGE_SIZE, *dptrs); - perf++; - } + t = ktime_get_ns(); + for (i = 0; i < REPS; i++) + algo->gen_syndrome(disks, BENCH_SIZE, dptrs); + t = max(ktime_get_ns() - t, 1); preempt_enable(); + /* bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s] */ + perf = div64_u64((u64)BENCH_SIZE * REPS * NR_SRCS * 1000, t); if (perf > bestgenperf) { bestgenperf = perf; best = algo; } - pr_info("raid6: %-8s gen() %5ld MB/s\n", algo->name, - (perf * HZ * (disks-2)) >> - (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2)); + pr_info("raid6: %-8s gen() %5lu MB/s\n", algo->name, perf); } if (!best) { @@ -197,28 +194,24 @@ static int raid6_choose_gen(void *(*const dptrs)[RAID6_TEST_DISKS], static_call_update(raid6_xor_syndrome_impl, best->xor_syndrome); pr_info("raid6: using algorithm %s gen() %ld MB/s\n", - best->name, - (bestgenperf * HZ * (disks - 2)) >> - (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2)); + best->name, bestgenperf); if (best->xor_syndrome) { - unsigned long perf = 0, j0, j1; + /* work on the second half of the disks */ + int start = (disks / 2) - 1, stop = disks - 3; + u64 t; 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++; - } + t = ktime_get_ns(); + for (i = 0; i < REPS; i++) + best->xor_syndrome(disks, start, stop, BENCH_SIZE, + dptrs); + t = max(ktime_get_ns() - t, 1); preempt_enable(); - pr_info("raid6: .... xor() %ld MB/s, rmw enabled\n", - (perf * HZ * (disks - 2)) >> - (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2 + 1)); + pr_info("raid6: .... xor() %llu MB/s, rmw enabled\n", + div64_u64((u64)BENCH_SIZE * REPS * NR_SRCS / 2 * 1000, + t)); } return 0; @@ -230,9 +223,9 @@ static int raid6_choose_gen(void *(*const dptrs)[RAID6_TEST_DISKS], static int __init raid6_select_algo(void) { - const int disks = RAID6_TEST_DISKS; + const int disks = NR_DISKS; + void *dptrs[NR_DISKS]; char *disk_ptr, *p; - void *dptrs[RAID6_TEST_DISKS]; int i, cycle; int error; @@ -243,7 +236,7 @@ static int __init raid6_select_algo(void) } /* prepare the buffer and fill it circularly with gfmul table */ - disk_ptr = kmalloc(PAGE_SIZE * RAID6_TEST_DISKS, GFP_KERNEL); + disk_ptr = kmalloc_array(NR_DISKS, BENCH_SIZE, GFP_KERNEL); if (!disk_ptr) { pr_err("raid6: Yikes! No memory available.\n"); return -ENOMEM; @@ -251,19 +244,19 @@ static int __init raid6_select_algo(void) p = disk_ptr; for (i = 0; i < disks; i++) - dptrs[i] = p + PAGE_SIZE * i; + dptrs[i] = p + BENCH_SIZE * i; - cycle = ((disks - 2) * PAGE_SIZE) / 65536; + cycle = ((disks - 2) * BENCH_SIZE) / 65536; for (i = 0; i < cycle; i++) { memcpy(p, raid6_gfmul, 65536); p += 65536; } - if ((disks - 2) * PAGE_SIZE % 65536) - memcpy(p, raid6_gfmul, (disks - 2) * PAGE_SIZE % 65536); + if ((disks - 2) * BENCH_SIZE % 65536) + memcpy(p, raid6_gfmul, (disks - 2) * BENCH_SIZE % 65536); /* select raid gen_syndrome function */ - error = raid6_choose_gen(&dptrs, disks); + error = raid6_choose_gen(dptrs, disks); kfree(disk_ptr); -- 2.53.0