From: "Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>,
"Singh, Jasvinder" <jasvinder.singh@intel.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] table: fix build error with gcc 8
Date: Mon, 9 Apr 2018 15:58:39 +0000 [thread overview]
Message-ID: <3EB4FA525960D640B5BDFFD6A3D891267BB3D389@IRSMSX108.ger.corp.intel.com> (raw)
In-Reply-To: <20180409080936.58ecb66c@xeon-e3>
> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Monday, April 9, 2018 4:10 PM
> To: Singh, Jasvinder <jasvinder.singh@intel.com>
> Cc: dev@dpdk.org; Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
> Subject: Re: [dpdk-dev] [PATCH] table: fix build error with gcc 8
>
> On Mon, 9 Apr 2018 13:49:48 +0100
> Jasvinder Singh <jasvinder.singh@intel.com> wrote:
>
> > Fix build error with gcc 8.0 due to cast between function types.
> > Fixes: 5a80bf0ae613 ("table: add cuckoo hash")
> >
> > Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
> > ---
> > lib/librte_table/rte_table_hash_cuckoo.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/librte_table/rte_table_hash_cuckoo.c
> b/lib/librte_table/rte_table_hash_cuckoo.c
> > index dcb4fe9..f7eae27 100644
> > --- a/lib/librte_table/rte_table_hash_cuckoo.c
> > +++ b/lib/librte_table/rte_table_hash_cuckoo.c
> > @@ -103,11 +103,13 @@ rte_table_hash_cuckoo_create(void *params,
> > return NULL;
> > }
> >
> > + void *hash_func = p->f_hash;
> > +
> > /* Create cuckoo hash table */
> > struct rte_hash_parameters hash_cuckoo_params = {
> > .entries = p->n_keys,
> > .key_len = p->key_size,
> > - .hash_func = (rte_hash_function)(p->f_hash),
> > + .hash_func = (rte_hash_function) hash_func,
> > .hash_func_init_val = p->seed,
> > .socket_id = socket_id,
> > .name = p->name
>
> This is just tricking the compiler into not complaining.
> I would really rather see the two hash functions made the same.
(Adding Bruce as well to consolidate all conversations in a single thread.)
What we want to do here is be able to use the librte_hash under the same API as the several hash table flavors implemented in librte_table.
Both of these libraries allow configuring the hash function per each hash table instance. Problem is: hash function in librte_hash has only 3 parameters (no key mask), while hash function in librte_table has 4 parameters (includes key mask). The key mask helps a lot for practical protocol implementations by avoiding key copy & pre-process on lookup.
So then: how to plug in librte_hash under the same API as the suite of hash tables in librte_table? We don't want to re-implement cuckoo hash from librte_hash, we simply want to invoke it as a low-level primitive, similarly to how the LPM and ACL tables are plugged into librte_table.
Solution is: as an exception, pass a 3-parameter hash function to cuckoo hash flavor under the librte_table. Maybe this should be documented better. This currently triggers a build warning with gcc 8, which is easy to fix, hence this trivial patch.
Ideally, for every 3-parameter hash function, I would like to generate the corresponding 4-parameter hash function on-the-fly, but unfortunately this is not what C language can do.
Of course, IMO the best solution is to add key mask support to librte_hash.
Regards,
Cristian
next prev parent reply other threads:[~2018-04-09 15:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-09 12:49 Jasvinder Singh
2018-04-09 12:59 ` Dumitrescu, Cristian
2018-04-09 13:09 ` Bruce Richardson
2018-04-09 14:51 ` Singh, Jasvinder
2018-04-09 15:28 ` Bruce Richardson
2018-04-09 16:41 ` Stephen Hemminger
2018-04-09 15:09 ` Stephen Hemminger
2018-04-09 15:58 ` Dumitrescu, Cristian [this message]
2018-04-09 16:38 ` Van Haaren, Harry
2018-04-09 16:43 ` Ferruh Yigit
2018-04-09 17:05 ` Dumitrescu, Cristian
2018-04-09 17:02 ` Dumitrescu, Cristian
2018-04-09 17:09 ` Ananyev, Konstantin
2018-04-09 17:26 ` Dumitrescu, Cristian
2018-04-10 12:32 ` Van Haaren, Harry
2018-04-10 11:43 ` Neil Horman
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