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Message-ID: <faa1075a-009c-e2c4-b76a-99352fd46e07@huaweicloud.com>
Date: Thu, 29 Jan 2026 11:26:38 +0800
From: Li Nan <linan666@...weicloud.com>
To: sunliming@...ux.dev, song@...nel.org, yukuai@...as.com
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
sunliming <sunliming@...inos.cn>
Subject: Re: [PATCH 1/3] lib/raid6: Divide the raid6 algorithm selection
process into two parts
在 2026/1/28 18:49, sunliming@...ux.dev 写道:
> From: sunliming <sunliming@...inos.cn>
>
> Divide the RAID6 algorithm selection process into two parts: fast selection
> and benchmark selection. To prepare for the asynchronous processing of
> the benchmark phase.
>
> Signed-off-by: sunliming <sunliming@...inos.cn>
> ---
> lib/raid6/algos.c | 76 +++++++++++++++++++++++++++++++----------------
> 1 file changed, 51 insertions(+), 25 deletions(-)
>
> diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
> index 799e0e5eac26..ac6a77b0ae1d 100644
> --- a/lib/raid6/algos.c
> +++ b/lib/raid6/algos.c
> @@ -134,7 +134,7 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
> static inline const struct raid6_recov_calls *raid6_choose_recov(void)
> {
> const struct raid6_recov_calls *const *algo;
> - const struct raid6_recov_calls *best;
> + const struct raid6_recov_calls *best = NULL;
>
> for (best = NULL, algo = raid6_recov_algos; *algo; algo++)
> if (!best || (*algo)->priority > best->priority)
> @@ -152,24 +152,44 @@ static inline const struct raid6_recov_calls *raid6_choose_recov(void)
> return best;
> }
>
> -static inline const struct raid6_calls *raid6_choose_gen(
> - void *(*const dptrs)[RAID6_TEST_DISKS], const int disks)
> +/* Quick selection: selects the first valid algorithm. */
> +static inline const struct raid6_calls *raid6_choose_gen_fast(void)
> +{
> + const struct raid6_calls *const *algo;
> + const struct raid6_calls *best = NULL;
> +
> + for (algo = raid6_algos; *algo; algo++) {
> + if ((*algo)->valid && !(*algo)->valid())
> + continue;
This logic is odd. We should select the highest-priority algorithm
instead of the first one. This was introduced by commit be85f93ae2df
("lib/raid6: add option to skip algorithm benchmarking").
After fix, this logic is identical to raid6_choose_recov(). Could we reuse
it after renaming the function?
> +
> + best = *algo;
> + break;
> + }
> +
> + if (best) {
> + raid6_call = *best;
> + pr_info("raid6: skipped pq benchmark and selected %s\n",
> + best->name);
> + } else {
> + pr_err("raid6: No valid algorithm found even for fast selection!\n");
> + }
> +
> + return best;
> +}
> +
> +static inline const struct raid6_calls *raid6_gen_benchmark(
> + void *(*const dptrs)[RAID6_TEST_DISKS], const int disks)
> {
> 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;
> + const struct raid6_calls *best = NULL;
>
> for (bestgenperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
> if (!best || (*algo)->priority >= best->priority) {
> if ((*algo)->valid && !(*algo)->valid())
> continue;
>
> - if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
> - best = *algo;
> - break;
> - }
> -
> perf = 0;
>
> preempt_disable();
> @@ -200,12 +220,6 @@ static inline const struct raid6_calls *raid6_choose_gen(
>
> 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)) >>
> @@ -235,16 +249,11 @@ static inline const struct raid6_calls *raid6_choose_gen(
> return best;
> }
>
> -
> /* Try to pick the best algorithm */
> /* This code uses the gfmul table as convenient data set to abuse */
> -
> -int __init raid6_select_algo(void)
> +static int raid6_choose_gen_benmark(const struct raid6_calls **gen_best)
> {
> const int disks = RAID6_TEST_DISKS;
> -
> - const struct raid6_calls *gen_best;
> - const struct raid6_recov_calls *rec_best;
> char *disk_ptr, *p;
> void *dptrs[RAID6_TEST_DISKS];
> int i, cycle;
> @@ -269,14 +278,31 @@ int __init raid6_select_algo(void)
> if ((disks - 2) * PAGE_SIZE % 65536)
> memcpy(p, raid6_gfmul, (disks - 2) * PAGE_SIZE % 65536);
>
> - /* select raid gen_syndrome function */
> - gen_best = raid6_choose_gen(&dptrs, disks);
> + *gen_best = raid6_gen_benchmark(&dptrs, disks);
> +
> + free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER);
> +
> + return 0;
> +}
> +
> +int __init raid6_select_algo(void)
> +{
> + int ret;
> + const struct raid6_calls *gen_best = NULL;
> + const struct raid6_recov_calls *rec_best = NULL;
> +
> + /* select raid gen_syndrome functions */
> + if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK))
> + gen_best = raid6_choose_gen_fast();
> + else {
> + ret = raid6_choose_gen_benmark(&gen_best);
'gen_best' is meaningless, use 'ret' directly. The input parameter of
raid6_choose_gen_benchmark() can be modified to void.
> + if (ret < 0)
> + return ret;
> + }
>
> /* select raid recover functions */
> rec_best = raid6_choose_recov();
>
> - free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER);
> -
> return gen_best && rec_best ? 0 : -EINVAL;
> }
>
--
Thanks,
Nan
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