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Subject[PATCH 4/4] lib/raid6: cleanup gen_syndrome function selection
Date
Reorders functions in raid6_algos as well as the preference check
to reduce the number of functions tested on initialization.

Also, creates symmetry between choosing the gen_syndrome functions
and choosing the recovery functions.

Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
---
lib/raid6/algos.c | 104 +++++++++++++++++++++++++++++------------------------
1 files changed, 57 insertions(+), 47 deletions(-)
diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index 5a7f802..589f5f5 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -34,10 +34,6 @@ struct raid6_calls raid6_call;
EXPORT_SYMBOL_GPL(raid6_call);

const struct raid6_calls * const raid6_algos[] = {
- &raid6_intx1,
- &raid6_intx2,
- &raid6_intx4,
- &raid6_intx8,
#if defined(__ia64__)
&raid6_intx16,
&raid6_intx32,
@@ -61,6 +57,10 @@ const struct raid6_calls * const raid6_algos[] = {
&raid6_altivec4,
&raid6_altivec8,
#endif
+ &raid6_intx1,
+ &raid6_intx2,
+ &raid6_intx4,
+ &raid6_intx8,
NULL
};

@@ -86,7 +86,7 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
#define time_before(x, y) ((x) < (y))
#endif

-static inline void raid6_choose_recov(void)
+static inline const struct raid6_recov_calls *raid6_choose_recov(void)
{
const struct raid6_recov_calls *const *algo;
const struct raid6_recov_calls *best;
@@ -103,62 +103,38 @@ static inline void raid6_choose_recov(void)
printk("raid6: using %s recovery algorithm\n", best->name);
} else
printk("raid6: Yikes! No recovery algorithm found!\n");
-}
-

-/* Try to pick the best algorithm */
-/* This code uses the gfmul table as convenient data set to abuse */
+ return best;
+}

-int __init raid6_select_algo(void)
+static inline const struct raid6_calls *raid6_choose_gen(
+ void *(*const dptrs)[(65536/PAGE_SIZE)+2], const int disks)
{
- const struct raid6_calls * const * algo;
- const struct raid6_calls * best;
- char *syndromes;
- void *dptrs[(65536/PAGE_SIZE)+2];
- int i, disks;
- unsigned long perf, bestperf;
- int bestprefer;
- unsigned long j0, j1;
-
- disks = (65536/PAGE_SIZE)+2;
- for ( i = 0 ; i < disks-2 ; i++ ) {
- dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
- }
-
- /* Normal code - use a 2-page allocation to avoid D$ conflict */
- syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
-
- if ( !syndromes ) {
- printk("raid6: Yikes! No memory available.\n");
- return -ENOMEM;
- }
-
- dptrs[disks-2] = syndromes;
- dptrs[disks-1] = syndromes + PAGE_SIZE;
+ unsigned long perf, bestperf, j0, j1;
+ const struct raid6_calls *const *algo;
+ const struct raid6_calls *best;

- bestperf = 0; bestprefer = 0; best = NULL;
+ for (bestperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
+ if (!best || (*algo)->prefer >= best->prefer) {
+ if ((*algo)->valid && !(*algo)->valid())
+ continue;

- for ( algo = raid6_algos ; *algo ; algo++ ) {
- if ( !(*algo)->valid || (*algo)->valid() ) {
perf = 0;

preempt_disable();
j0 = jiffies;
- while ( (j1 = jiffies) == j0 )
+ while ((j1 = jiffies) == j0)
cpu_relax();
while (time_before(jiffies,
j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
- (*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
+ (*algo)->gen_syndrome(disks, PAGE_SIZE, *dptrs);
perf++;
}
preempt_enable();

- if ( (*algo)->prefer > bestprefer ||
- ((*algo)->prefer == bestprefer &&
- perf > bestperf) ) {
- best = *algo;
- bestprefer = best->prefer;
+ if (perf > bestperf) {
bestperf = perf;
+ best = *algo;
}
printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
(perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
@@ -173,12 +149,46 @@ int __init raid6_select_algo(void)
} else
printk("raid6: Yikes! No algorithm found!\n");

- free_pages((unsigned long)syndromes, 1);
+ 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)
+{
+ const int disks = (65536/PAGE_SIZE)+2;
+
+ const struct raid6_calls *gen_best;
+ const struct raid6_recov_calls *rec_best;
+ char *syndromes;
+ void *dptrs[(65536/PAGE_SIZE)+2];
+ int i;
+
+ for (i = 0; i < disks-2; i++)
+ dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
+
+ /* Normal code - use a 2-page allocation to avoid D$ conflict */
+ syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
+
+ if (!syndromes) {
+ printk("raid6: Yikes! No memory available.\n");
+ return -ENOMEM;
+ }
+
+ dptrs[disks-2] = syndromes;
+ dptrs[disks-1] = syndromes + PAGE_SIZE;
+
+ /* select raid gen_syndrome function */
+ gen_best = raid6_choose_gen(&dptrs, disks);

/* select raid recover functions */
- raid6_choose_recov();
+ rec_best = raid6_choose_recov();
+
+ free_pages((unsigned long)syndromes, 1);

- return best ? 0 : -EINVAL;
+ return gen_best && rec_best ? 0 : -EINVAL;
}

static void raid6_exit(void)
--
1.7.8.5


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