[ovs-dev] [PATCH v2] xlate: Use dp_hash for select groups.

[Jarno Rajahalme]

Thanks for the fix!

While I was working with tightening the parsing, I found that I had earlier introduced a bug that crashes ovs-ofctl when a parsing error is found after parsing ‘fields’, essentially a double free. I sent a v3 fixing this, documenting the parsing tightening and then rebasing this patch with this fix, additional documentation and with the NEWS piece moved to the post-2.6b section.

  Jarno

> On Sep 14, 2016, at 8:53 PM, Ben Pfaff <blp at ovn.org> wrote:
> 
> On Wed, Sep 14, 2016 at 08:51:42PM -0700, Ben Pfaff wrote:
>> On Mon, Sep 12, 2016 at 04:16:08PM -0700, Jarno Rajahalme wrote:
>>> Add a new select group selection method "dp_hash", which uses minimal
>>> number of bits from the datapath calculated packet hash to inform the
>>> select group bucket selection.  This makes the datapath flows more
>>> generic resulting in less upcalls to userspace, but adds recirculation
>>> prior to group selection.
>>> 
>>> Signed-off-by: Jarno Rajahalme <jarno at ovn.org>
>>> ---
>>> v2: Rebase and documentation.
>> 
>> Thanks for adding the documentation!  It describes the syntax, which is
>> useful.  To make it even more helpful, I would suggest adding some
>> advice to the user to explain when one might best choose one or the
>> other.
>> 
>> I think that the dp_hash method ignores fields specified by the user if
>> any are given, so the documentation might mention that for dp_hash the
>> "fields" option should be omitted.
>> 
>> Thanks!
>> 
>> Acked-by: Ben Pfaff <blp at ovn.org>
> 
> Oh, I forgot to say that I get a compiler warning:
> 
>    ../ofproto/ofproto-dpif-xlate.c: In function 'xlate_dp_hash_select_group':
>    ../ofproto/ofproto-dpif-xlate.c:3410:32: error: variable 'buckets' set but not used [-Werror=unused-but-set-variable]
>             const struct ovs_list *buckets;
> 
> Fixed by:
> 
> diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
> index c83132c..a74daa7 100644
> --- a/ofproto/ofproto-dpif-xlate.c
> +++ b/ofproto/ofproto-dpif-xlate.c
> @@ -3407,10 +3407,8 @@ xlate_dp_hash_select_group(struct xlate_ctx *ctx, struct group_dpif *group)
> 
>         ctx_trigger_recirculate_with_hash(ctx, param >> 32, (uint32_t)param);
>     } else {
> -        const struct ovs_list *buckets;
>         uint32_t n_buckets;
> -
> -        buckets = group_dpif_get_buckets(group, &n_buckets);
> +        group_dpif_get_buckets(group, &n_buckets);
>         if (n_buckets) {
>             /* Minimal mask to cover the number of buckets. */
>             uint32_t mask = (1 << log_2_ceil(n_buckets)) - 1;