On Mon, Jun 5, 2017 at 8:24 AM, Bala Manoharan
<bala.manoha...@linaro.org> wrote:
> Regards,
> Bala
>
>
> On 5 June 2017 at 18:24, Bill Fischofer <bill.fischo...@linaro.org> wrote:
>> On Mon, Jun 5, 2017 at 7:32 AM, Stanislaw Kardach <k...@semihalf.com> wrote:
>>>
>>>
>>> Best Regards,
>>> Stanislaw Kardach
>>>
>>> On 06/05/2017 02:27 PM, Balasubramanian Manoharan wrote:
>>>> Adds threshold limit of the pool to the pool parameters.
>>>> This threshold limit is a percentage of total size of the pool.
>>>>
>>>> Signed-off-by: Balasubramanian Manoharan <bala.manoha...@linaro.org>
>>>> ---
>>>> include/odp/api/spec/pool.h | 32 ++++++++++++++++++++++++++++++++
>>>> 1 file changed, 32 insertions(+)
>>>>
>>>> diff --git a/include/odp/api/spec/pool.h b/include/odp/api/spec/pool.h
>>>> index 6fc5b6b..1c1ebe4 100644
>>>> --- a/include/odp/api/spec/pool.h
>>>> +++ b/include/odp/api/spec/pool.h
>>>> @@ -20,6 +20,7 @@ extern "C" {
>>>> #endif
>>>>
>>>> #include <odp/api/std_types.h>
>>>> +#include <odp/api/support.h>
>>>>
>>>> /** @defgroup odp_pool ODP POOL
>>>> * Operations on a pool.
>>>> @@ -127,6 +128,9 @@ typedef struct odp_pool_capability_t {
>>>> * The value of zero means that limited only by the available
>>>> * memory size for the pool. */
>>>> uint32_t max_uarea_size;
>>>> +
>>>> + /** Pool Threshold limit support */
>>>> + odp_support_t pool_threshold_limit;
>>>> } pkt;
>>>>
>>>> /** Timeout pool capabilities */
>>>> @@ -214,6 +218,17 @@ typedef struct odp_pool_param_t {
>>>> defined by pool capability pkt.max_uarea_size.
>>>> Specify as 0 if no user area is needed. */
>>>> uint32_t uarea_size;
>>>> +
>>>> + /** Pool threshold limit in percentage
>>>> + *
>>>> + * This value denotes the threshold limit of the
>>>> pool in
>>>> + * percentage of the total size of the pool and is
>>>> used
>>>> + * to configure the Random Early Discard (RED).
>>>> + * When the number of packets in the pool is greater
>>>> + * than this value RED is initiated in the pool and
>>>> + * further incoming packets to the pool are dropped
>>>> in
>>>> + * a random sequence. */
>>>> + uint8_t threshold_limit;
>>> Is threshold limit "a percentage of total size of the pool" (hence I
>>> guess 0-100) or rather an absolute value that triggers RED?
>>
>> Do we want to tie this specifically to RED or try to make things more
>> general? There are many types of flow/congestion control algorithms
>> that can be used so perhaps that should be better parameterized? Also,
>> when specifying thresholds it's customary to set high and low
>> watermarks to provide hysteresis. Some algorithms also need more than
>> one data point to control the curves, so again this suggests that we
>> need additional parameterization for this.
>
> The idea is to have a configuration value for enabling or disabling
> Random Early Discard in the packet ingress which could be configured
> either in the queue or in pool depending on the implementation. I
> actually thought about having a higher /lower watermark but went
> against this since the logic I have followed in this proposal is to
> have a mechanism to start or stop the RED, IMO a single threshold
> value is sufficient and RED gets initiated when packet is greater than
> the threshold and is disabled when the packet limit on the pool is
> lesser than this threshold.
A single value may work for basic RED, but if you want to support
other options like PFC then you need more than a single value or else
you wind up "stuttering" around the single value when utilization is
very close to it. That's because PFC doesn't just do something with a
packet--it actively transmits pause frames.
>
>>
>>>
>>>> } pkt;
>>>>
>>>> /** Parameters for timeout pools */
>>>> @@ -329,6 +344,23 @@ uint64_t odp_pool_to_u64(odp_pool_t hdl);
>>>> void odp_pool_param_init(odp_pool_param_t *param);
>>>>
>>>> /**
>>>> + * Set threshold limit of the pool
>>>> + *
>>>> + * Set the threshold limit of the pool as a percentage of the total
>>>> + * size of the pool. This value is used to configure Random Early
>>>> Discard(RED)
>>>> + * parameters of the pool and any incoming packets to the pool after
>>>> reaching
>>>> + * this threshold is dropped in a random sequence.
>>>> + *
>>>> + * @param pool Pool handle
>>>> + * @param threshold_limit Threshold limit of the pool.
>>>> + *
>>>> + * @retval 0 on success
>>>> + * @retval -1 on failure
>>>> + */
>>>> +
>>>> +int odp_pool_threshold_limit(odp_pool_t pool, uint8_t threshold_limit);
>>>> +
>>>> +/**
>>>> * @}
>>>> */
>>>>
>>>>
