-----Original Message-----
From: Michel Machado <mic...@digirati.com.br>
Sent: Tuesday, August 21, 2018 7:42 AM
To: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>; Fu, Qiaobin
<qiaob...@bu.edu>; Richardson, Bruce <bruce.richard...@intel.com>; De Lara
Guarch, Pablo <pablo.de.lara.gua...@intel.com>
Cc: dev@dpdk.org; Doucette, Cody, Joseph <douce...@bu.edu>; Wang, Yipeng1
<yipeng1.w...@intel.com>; Wiles, Keith <keith.wi...@intel.com>; Gobriel, Sameh
<sameh.gobr...@intel.com>; Tai, Charlie <charlie....@intel.com>; Stephen
Hemminger <step...@networkplumber.org>; nd <n...@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2] hash table: add an iterator over conflicting
entries
On 08/21/2018 01:10 AM, Honnappa Nagarahalli wrote:
> On 08/17/2018 03:41 PM, Honnappa Nagarahalli wrote:
>> Can you elaborate more on using ' struct rte_conflict_iterator_state' as the
>> argument for the API?
>>
>> If the API signature is changed to: rte_hash_iterate_conflict_entries (const
>> struct rte_hash *h, void **key, void **data, const hash_sig_t sig, struct
>> rte_conflict_iterator_state *state) - it will be inline with the existing
>> APIs. Contents of 'state' must be initialized to 0 for the first call. This
>> will also avoid creating 'rte_hash_iterator_conflict_entries_init' API.
>
> Testing `state' every time rte_hash_iterate_conflict_entries() is
> called to find out if it's the first call of the iterator will
> possibly add some small, but unnecessary, overhead on
> rte_hash_iterate_conflict_entries() and constraints on struct
> rte_conflict_iterator_state. Moreover,
> rte_hash_iterator_conflict_entries_init() enables one to easily add
> variations of the init function to initialize the state (e.g. using a key
> instead of a sig) and still use the exactly same iterator.
>
> IMO, I think, this over-head will be trivial. Looking at the function
> 'rte_hash_iterate_conflict_entries' the check for '(__state->vnext <
> RTE_HASH_BUCKET_ENTRIES * 2)' already exists. If the primary/secondary bucket
> indices are calculated as well in 'rte_hash_iterate_conflict_entries' API
> ('rte_hash_iterate' API does such calculations), storing them in the state
> can be avoided. I am wondering if it makes sense to benchmark with these
> changes and then take a decision?
We have come up with the init function and struct
rte_conflict_iterator_state in v2 to make the new iterator as future proof to a
change of the underlying algorithm as possible. But going through your
feedback, it seems to me that your top concern is to not deviate much of the
current interface of rte_hash_iterate(). We are fine with pushing v3 using the
interface you've suggested to avoid the init function and struct
rte_conflict_iterator_state:
int32_t
rte_hash_iterate_conflict_entries__with_hash(const struct rte_hash *h, const
void **key, void **data, hash_sig_t sig, uint32_t *next);
Yes, this is my primary concern. Above signature will conform to what we have
currently. If APIs have to change because of the change in underlying algorithm
we can do it when it happens (with the better understanding of the situation at
that time).
I have to add that I liked your idea of 64B state. But that also means it is
not in line with rte_hash_iterate(). We should remember to do it in the future
if we happen to change the API signature.
[ ]'s
Michel Machado
