On Tue, Apr 17, 2018 at 01:03:17PM -0700, Ben Pfaff wrote:
> On Mon, Apr 16, 2018 at 04:26:27PM +0200, Jan Scheurich wrote:
> > The current implementation of the "dp_hash" selection method suffers
> > from two deficiences: 1. The hash mask and hence the number of dp_hash
> > values is just large enough to cover the number of group buckets, but
> > does not consider the case that buckets have different weights. 2. The
> > xlate-time selection of best bucket from the masked dp_hash value often
> > results in bucket load distributions that are quite different from the
> > bucket weights because the number of available masked dp_hash values
> > is too small (2-6 bits compared to 32 bits of a full hash in the default
> > hash selection method).
>
> Clang gives me the following errors:
>
> ../ofproto/ofproto-dpif.c:4792:32: error: unknown warning group
> '-Wmaybe-uninitialized', ignored [-Werror,-Wunknown-pragmas]
> ../ofproto/ofproto-dpif.c:4814:33: error: initializing 'struct
> ofputil_group_props *' with an expression of type 'const struct
> ofputil_group_props *' discards qualifiers
> [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
How about this approach, which should cleanly eliminate the warning?
diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index e1a5c097f3aa..362339a4abb4 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -4780,22 +4780,17 @@ group_setup_dp_hash_table(struct group_dpif *group,
size_t max_hash)
/* Use Webster method to distribute hash values over buckets. */
for (int hash = 0; hash < n_hash; hash++) {
- double max_val = 0.0;
- struct webster *winner;
- for (i = 0; i < n_buckets; i++) {
- if (webster[i].value > max_val) {
- max_val = webster[i].value;
+ struct webster *winner = &webster[0];
+ for (i = 1; i < n_buckets; i++) {
+ if (webster[i].value > winner->value) {
winner = &webster[i];
}
}
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
/* winner is a reference to a webster[] element initialized above. */
winner->divisor += 2;
winner->value = (double) winner->bucket->weight / winner->divisor;
group->hash_map[hash] = winner->bucket;
winner->bucket->aux++;
-#pragma GCC diagnostic pop
}
LIST_FOR_EACH (bucket, list_node, &group->up.buckets) {
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