> On Feb 22, 2024, at 6:39 AM, Abdullah Ömer Yamaç <aomerya...@gmail.com> wrote:
>
> As a final decision, I will add a new hash API that forces the reclaim. Is it
> ok for everyone?
Ack from my side
>
> On Thu, Feb 22, 2024 at 5:37 AM Honnappa Nagarahalli
> <honnappa.nagaraha...@arm.com> wrote:
>
>
> > On Feb 21, 2024, at 3:51 PM, Abdullah Ömer Yamaç <aomerya...@gmail.com>
> > wrote:
> >
> >
> >
> > On Wed, Feb 21, 2024 at 6:24 AM Honnappa Nagarahalli
> > <honnappa.nagaraha...@arm.com> wrote:
> >
> >
> > > On Feb 20, 2024, at 12:58 PM, Abdullah Ömer Yamaç <aomerya...@gmail.com>
> > > wrote:
> > >
> > > I appreciate that you gave me suggestions and comments. I will make
> > > changes according to all your recommendations, but before that, I want to
> > > make everyone's minds clear. Then, I will apply modifications.
> > >
> > > On Tue, Feb 20, 2024 at 2:35 AM Honnappa Nagarahalli
> > > <honnappa.nagaraha...@arm.com> wrote:
> > >
> > >
> > > > On Feb 19, 2024, at 3:28 PM, Abdullah Ömer Yamaç <aomerya...@gmail.com>
> > > > wrote:
> > > >
> > > > Hello,
> > > >
> > > > Let me explain a use case;
> > > >
> > > > I have a hash table whose key value is IP addresses, and data (let's
> > > > say the username of the IP) is related to the IP address. The key point
> > > > is matching these data with flows. Flows are dynamic, and this hash
> > > > table is dynamic, as well; both can change anytime. For example, when a
> > > > flow starts, we look up the hash table with the corresponding IP and
> > > > retrieve the username. We need to hold this username until the flow
> > > > terminates, although we removed this IP key from the hash table
> > > > (multithread). That's why we have RCU and defer queue is necessary for
> > > > high performance. In my application, I need to know the number of
> > > > IP-username entries. These numbers can be calculated by rte_hash_count
> > > > - defer queue size.
> > > The entries in the defer queue are not reclaimed (there is a probability
> > > that all of them can be reclaimed) and hence they are not available for
> > > allocation. So, rte_hash_count - defer queue size might not give you the
> > > correct number you are expecting.
> > >
> > > Currently, there is no API in hash library that forces a reclaim. Does it
> > > makes sense to have an API that just does the reclaim (and returns the
> > > number of entries pending in the defer queue)? A call to rte_hash_count
> > > should provide the exact count you are looking for.
> > > You are right; no API in the hash library forces a reclaim. In my
> > > application, I periodically call rte_count to retrieve hash size, and
> > > this data is shown in my GUI. So that means I need to call regularly
> > > reclaim. I am trying to figure out which is better, calling reclaim or
> > > retrieving the defer queue size. Any comment about this?
> > Retrieving the defer queue size will be cheaper. However, calling the
> > reclaim API will ensure the entries are freed hence providing an accurate
> > number. Calling the reclaim API on an empty defer queue does not consume
> > many cycles. If needed we could add a check for empty defer queue in the
> > reclaim API and return early.
> >
> > I am also wondering if a reclaim API in hash library is needed. Why not
> > call rte_rcu_qsbr_dq_reclaim API from the application?
> > The reason is simple. struct rte_hash *h is an internal structure and we
> > cannot access the h->dq. So it is not possible to call reclaim.
> Ack. This will be just a wrapper around the rte_rcu_qsbr_dq_reclaim.
>
> >
> >
> > > >
> > > > I think if you need a non-blocking and multithreaded hash table, an
> > > > RCU-enabled hash table is necessary. Also, this API is necessary if you
> > > > need to get the actual matchable size.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > On Mon, Feb 19, 2024 at 8:36 PM Medvedkin, Vladimir
> > > > <vladimir.medved...@intel.com> wrote:
> > > > Hi Abdullah,
> > > >
> > > > Could you please tell more about use cases where this API may be useful?
> > > >
> > > > >a new API to get the hidden key count in the hash table if the rcu
> > > > >qsbr is enabled
> > > >
> > > > Here in commit message and down below in doxygen comments, I think this
> > > > statement should be more specific because rcu can be created with
> > > > RTE_HASH_QSBR_MODE_SYNC mode i.e. without defer queue.
> > > >
> > > > Also, new API must be reflected in release notes
> > > >
> > > > On 07/02/2024 15:33, Abdullah Ömer Yamaç wrote:
> > > > > This patch introduce a new API to get the hidden key count in the hash
> > > > > table if the rcu qsbr is enabled. When using rte_hash_count with rcu
> > > > > qsbr enabled, it will return the number of elements that are not in
> > > > > the
> > > > > free queue. Unless rte_rcu_qsbr_dq_reclaim is called, the number of
> > > > > elements in the defer queue will not be counted and freed. Therefore I
> > > > > added a new API to get the number of hidden (defer queue) elements
> > > > > in the hash table. Then the user can calculate the total number of
> > > > > elements that are available in the hash table.
> > > > >
> > > > > Signed-off-by: Abdullah Ömer Yamaç <aomerya...@gmail.com>
> > > > >
> > > > > ---
> > > > > Cc: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> > > > > Cc: Yipeng Wang <yipeng1.w...@intel.com>
> > > > > Cc: Sameh Gobriel <sameh.gobr...@intel.com>
> > > > > Cc: Bruce Richardson <bruce.richard...@intel.com>
> > > > > Cc: Vladimir Medvedkin <vladimir.medved...@intel.com>
> > > > > ---
> > > > > lib/hash/rte_cuckoo_hash.c | 9 +++++++++
> > > > > lib/hash/rte_hash.h | 13 +++++++++++++
> > > > > lib/hash/version.map | 1 +
> > > > > lib/rcu/rte_rcu_qsbr.c | 8 ++++++++
> > > > > lib/rcu/rte_rcu_qsbr.h | 11 +++++++++++
> > > > > lib/rcu/version.map | 1 +
> > > > > 6 files changed, 43 insertions(+)
> > > > >
> > > > > diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
> > > > > index 70456754c4..3553f3efc7 100644
> > > > > --- a/lib/hash/rte_cuckoo_hash.c
> > > > > +++ b/lib/hash/rte_cuckoo_hash.c
> > > > > @@ -555,6 +555,15 @@ rte_hash_max_key_id(const struct rte_hash *h)
> > > > > return h->entries;
> > > > > }
> > > > >
> > > > > +int32_t
> > > > > +rte_hash_dq_count(const struct rte_hash *h)
> > > > > +{
> > > > > + if (h->dq == NULL)
> > > > input arguments must be checked since this is a public API, the same is
> > > > true for rte_rcu_qsbr_dq_count()
> > > > > + return -EINVAL;
> > > > why not just return 0?
> > > > > +
> > > > > + return rte_rcu_qsbr_dq_count(h->dq);
> > > > > +}
> > > > > +
> > > > > int32_t
> > > > > rte_hash_count(const struct rte_hash *h)
> > > > > {
> > > > > diff --git a/lib/hash/rte_hash.h b/lib/hash/rte_hash.h
> > > > > index 7ecc021111..8ea97e297d 100644
> > > > > --- a/lib/hash/rte_hash.h
> > > > > +++ b/lib/hash/rte_hash.h
> > > > > @@ -193,6 +193,19 @@ rte_hash_free(struct rte_hash *h);
> > > > > void
> > > > > rte_hash_reset(struct rte_hash *h);
> > > > >
> > > > > +
> > > > > +/**
> > > > > + * Return the number of records in the defer queue of the hash table
> > > > > + * if RCU is enabled.
> > > > > + * @param h
> > > > > + * Hash table to query from
> > > > > + * @return
> > > > > + * - -EINVAL if parameters are invalid
> > > > > + * - A value indicating how many records were inserted in the
> > > > > table.
> > > > did you mean how many records are kept in defer queue?
> > > > > + */
> > > > > +int32_t
> > > > > +rte_hash_dq_count(const struct rte_hash *h);
> > > > > +
> > > > > /**
> > > > > * Return the number of keys in the hash table
> > > > > * @param h
> > > > > diff --git a/lib/hash/version.map b/lib/hash/version.map
> > > > > index 6b2afebf6b..7f7b158cf1 100644
> > > > > --- a/lib/hash/version.map
> > > > > +++ b/lib/hash/version.map
> > > > > @@ -9,6 +9,7 @@ DPDK_24 {
> > > > > rte_hash_add_key_with_hash;
> > > > > rte_hash_add_key_with_hash_data;
> > > > > rte_hash_count;
> > > > > + rte_hash_dq_count;
> > > > new API must introduced as an experimental API. The same is true for
> > > > rte_rcu_qsbr_dq_count()
> > > > > rte_hash_crc32_alg;
> > > > > rte_hash_crc_set_alg;
> > > > > rte_hash_create;
> > > > > diff --git a/lib/rcu/rte_rcu_qsbr.c b/lib/rcu/rte_rcu_qsbr.c
> > > > > index bd0b83be0c..89f8da4c4c 100644
> > > > > --- a/lib/rcu/rte_rcu_qsbr.c
> > > > > +++ b/lib/rcu/rte_rcu_qsbr.c
> > > > > @@ -450,6 +450,14 @@ rte_rcu_qsbr_dq_reclaim(struct rte_rcu_qsbr_dq
> > > > > *dq, unsigned int n,
> > > > > return 0;
> > > > > }
> > > > >
> > > > > +/**
> > > > > + * Return the number of entries in a defer queue.
> > > > > + */
> > > > > +unsigned int rte_rcu_qsbr_dq_count(struct rte_rcu_qsbr_dq *dq)
> > > > > +{
> > > Please validate dq here.
> > >
> > > > > + return rte_ring_count(dq->r);
> > > > > +}
> > > > > +
> > > > > /* Delete a defer queue. */
> > > > > int
> > > > > rte_rcu_qsbr_dq_delete(struct rte_rcu_qsbr_dq *dq)
> > > > > diff --git a/lib/rcu/rte_rcu_qsbr.h b/lib/rcu/rte_rcu_qsbr.h
> > > > > index 23c9f89805..ed5a590edd 100644
> > > > > --- a/lib/rcu/rte_rcu_qsbr.h
> > > > > +++ b/lib/rcu/rte_rcu_qsbr.h
> > > > > @@ -794,6 +794,17 @@ int
> > > > > rte_rcu_qsbr_dq_reclaim(struct rte_rcu_qsbr_dq *dq, unsigned int n,
> > > > > unsigned int *freed, unsigned int *pending, unsigned int
> > > > > *available);
> > > > >
> > > > > +/**
> > > > > + * Return the number of entries in a defer queue.
> > > > > + *
> > > > > + * @param dq
> > > > > + * Defer queue.
> > > > > + * @return
> > > > > + * The number of entries in the defer queue.
> > > > > + */
> > > > > +unsigned int
> > > > > +rte_rcu_qsbr_dq_count(struct rte_rcu_qsbr_dq *dq);
> > > Agree on the need for this API in RCU
> > >
> > > > > +
> > > > > /**
> > > > > * Delete a defer queue.
> > > > > *
> > > > > diff --git a/lib/rcu/version.map b/lib/rcu/version.map
> > > > > index 982ffd59d9..f410ab41e7 100644
> > > > > --- a/lib/rcu/version.map
> > > > > +++ b/lib/rcu/version.map
> > > > > @@ -5,6 +5,7 @@ DPDK_24 {
> > > > > rte_rcu_qsbr_dq_create;
> > > > > rte_rcu_qsbr_dq_delete;
> > > > > rte_rcu_qsbr_dq_enqueue;
> > > > > + rte_rcu_qsbr_dq_count;
> > > > > rte_rcu_qsbr_dq_reclaim;
> > > > > rte_rcu_qsbr_dump;
> > > > > rte_rcu_qsbr_get_memsize;
> > > >
> > > > --
> > > > Regards,
> > > > Vladimir
> > > >
> > >
> >
>
