[dpdk-dev] [PATCH 2/2] Adding the routines rte_pktmbuf_alloc_bulk() and rte_pktmbuf_free_bulk()

Wiles, Roger Keith keith.wiles at windriver.com
Mon Oct 6 18:13:16 CEST 2014


On Oct 6, 2014, at 10:54 AM, Ananyev, Konstantin <konstantin.ananyev at intel.com> wrote:

>> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Bruce Richardson
>> Sent: Monday, October 06, 2014 3:54 PM
>> To: Wiles, Roger Keith (Wind River)
>> Cc: dev at dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH 2/2] Adding the routines rte_pktmbuf_alloc_bulk() and rte_pktmbuf_free_bulk()
>> 
>> On Mon, Oct 06, 2014 at 03:50:38PM +0100, Wiles, Roger Keith wrote:
>>> Hi Bruce,
>>> 
>>> Do I need to reject the for the new routines or just make sure the vector driver does not get updated to use those routines?
>>> 
>> 
>> The new routines are probably useful in the general case. I see no issue
>> with having them in the code, so long as the vector driver is not modified
>> to use them.
> 
> I 'd say the same thing for non-vector RX/TX PMD code-paths too.
> 
> BTW, are the new functions comments valid?
> 
> + * @return
> + *   - 0 if the number of mbufs allocated was ok
> + *   - <0 is an ERROR.
> + */
> +static inline int __rte_mbuf_raw_alloc_bulk(
> 
> Though, as I can see __rte_mbuf_raw_alloc_bulk() returns either:
> - number of  allocated mbuf (cnt)
> - negative error code

Let me fix up the comments.
> 
> And:
> + * @return
> + *   - The number of valid mbufs pointers in the m_list array.
> + *   - Zero if the request cnt could not be allocated.
> + */
> +static inline int __attribute__((always_inline))
> +rte_pktmbuf_alloc_bulk(struct rte_mempool *mp, struct rte_mbuf *m_list[], int16_t cnt)
> +{
> +     return __rte_mbuf_raw_alloc_bulk(mp, m_list, cnt);
> +}
> 
> Shouldn't be "less than zero if the request cnt could not be allocated."?
> 
> BTW, is there any point to have __rte_mbuf_raw_alloc_bulk() at all?
> After all, as you are calling rte_pktmbuf_reset() inside it, it doesn't look __raw__ any more.
> Might be just put its content into rte_pktmbuf_alloc_bulk() and get rid of it.
> 
I was just following the non-bulk routine style __rte_mbuf_raw_alloc(), but I can pull that into a single routine.

> Also wonder, what is the advantage of having multiple counters inside the same loop?
> i.e:
> +             for(i = 0; i < cnt; i++) {
> +                     m = *m_list++;
> 
> Why not just:
> 
> for(i = 0; i < cnt; i++) {
>    m = &m_list[i];
> 
> Same for free:
> +     while(npkts--)
> +             rte_pktmbuf_free(*m_list++);
> 
> While not just:
> for (i = 0; i < npkts; i++)
>      rte_pktmbuf_free(&m_list[i]);

Maybe I have it wrong or the compilers are doing the right thing now, but at one point the &m_list[i] would cause the compiler to generate a shift or multiple of ‘i’ and then add it to the base of m_list. If that is not the case anymore then I can update the code as you suggested. Using the *m_list++ just adds the size of a pointer to a register and continues.
> 
> Konstantin
> 
>> 
>> /Bruce
>> 
>>> Thanks
>>> ++Keith
>>> 
>>> On Oct 6, 2014, at 3:56 AM, Richardson, Bruce <bruce.richardson at intel.com> wrote:
>>> 
>>>> 
>>>> 
>>>>> -----Original Message-----
>>>>> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Keith Wiles
>>>>> Sent: Sunday, October 05, 2014 12:10 AM
>>>>> To: dev at dpdk.org
>>>>> Subject: [dpdk-dev] [PATCH 2/2] Adding the routines rte_pktmbuf_alloc_bulk()
>>>>> and rte_pktmbuf_free_bulk()
>>>>> 
>>>>> Minor helper routines to mirror the mempool routines and remove the code
>>>>> from applications. The ixgbe_rxtx_vec.c routine could be changed to use
>>>>> the ret_pktmbuf_alloc_bulk() routine inplace of rte_mempool_get_bulk().
>>>>> 
>>>> 
>>>> I believe such a change would cause a performance regression, as the extra init code in the alloc_bulk() function would take
>> additional cycles and is not needed. The vector routines use the mempool function directly, so that there is no overhead of mbuf
>> initialization, as the vector routines use their additional "knowledge" of what the mbufs will be used for to init them in a faster manner
>> than can be done inside the mbuf library.
>>>> 
>>>> /Bruce
>>>> 
>>>>> Signed-off-by: Keith Wiles <keith.wiles at windriver.com>
>>>>> ---
>>>>> lib/librte_mbuf/rte_mbuf.h | 77
>>>>> ++++++++++++++++++++++++++++++++++++++++++++++
>>>>> 1 file changed, 77 insertions(+)
>>>>> 
>>>>> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
>>>>> index 1c6e115..f298621 100644
>>>>> --- a/lib/librte_mbuf/rte_mbuf.h
>>>>> +++ b/lib/librte_mbuf/rte_mbuf.h
>>>>> @@ -546,6 +546,41 @@ static inline void rte_pktmbuf_reset(struct rte_mbuf
>>>>> *m)
>>>>> }
>>>>> 
>>>>> /**
>>>>> + * @internal Allocate a list of mbufs from mempool *mp*.
>>>>> + * The use of that function is reserved for RTE internal needs.
>>>>> + * Please use rte_pktmbuf_alloc_bulk().
>>>>> + *
>>>>> + * @param mp
>>>>> + *   The mempool from which mbuf is allocated.
>>>>> + * @param m_list
>>>>> + *   The array to place the allocated rte_mbufs pointers.
>>>>> + * @param cnt
>>>>> + *   The number of mbufs to allocate
>>>>> + * @return
>>>>> + *   - 0 if the number of mbufs allocated was ok
>>>>> + *   - <0 is an ERROR.
>>>>> + */
>>>>> +static inline int __rte_mbuf_raw_alloc_bulk(struct rte_mempool *mp, struct
>>>>> rte_mbuf *m_list[], int cnt)
>>>>> +{
>>>>> +     struct rte_mbuf *m;
>>>>> +     int             ret;
>>>>> +
>>>>> +     ret = rte_mempool_get_bulk(mp, (void **)m_list, cnt);
>>>>> +     if ( ret == 0 ) {
>>>>> +             int             i;
>>>>> +             for(i = 0; i < cnt; i++) {
>>>>> +                     m = *m_list++;
>>>>> +#ifdef RTE_MBUF_REFCNT
>>>>> +                     rte_mbuf_refcnt_set(m, 1);
>>>>> +#endif /* RTE_MBUF_REFCNT */
>>>>> +                     rte_pktmbuf_reset(m);
>>>>> +             }
>>>>> +             ret = cnt;
>>>>> +     }
>>>>> +     return ret;
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> * Allocate a new mbuf from a mempool.
>>>>> *
>>>>> * This new mbuf contains one segment, which has a length of 0. The pointer
>>>>> @@ -671,6 +706,32 @@ __rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
>>>>> }
>>>>> 
>>>>> /**
>>>>> + * Allocate a list of mbufs from a mempool into a mbufs array.
>>>>> + *
>>>>> + * This mbuf list contains one segment per mbuf, which has a length of 0. The
>>>>> pointer
>>>>> + * to data is initialized to have some bytes of headroom in the buffer
>>>>> + * (if buffer size allows).
>>>>> + *
>>>>> + * The routine is just a simple wrapper routine to reduce code in the application
>>>>> and
>>>>> + * provide a cleaner API for multiple mbuf requests.
>>>>> + *
>>>>> + * @param mp
>>>>> + *   The mempool from which the mbuf is allocated.
>>>>> + * @param m_list
>>>>> + *   An array of mbuf pointers, cnt must be less then or equal to the size of the
>>>>> list.
>>>>> + * @param cnt
>>>>> + *   Number of slots in the m_list array to fill.
>>>>> + * @return
>>>>> + *   - The number of valid mbufs pointers in the m_list array.
>>>>> + *   - Zero if the request cnt could not be allocated.
>>>>> + */
>>>>> +static inline int __attribute__((always_inline))
>>>>> +rte_pktmbuf_alloc_bulk(struct rte_mempool *mp, struct rte_mbuf *m_list[],
>>>>> int16_t cnt)
>>>>> +{
>>>>> +     return __rte_mbuf_raw_alloc_bulk(mp, m_list, cnt);
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> * Free a segment of a packet mbuf into its original mempool.
>>>>> *
>>>>> * Free an mbuf, without parsing other segments in case of chained
>>>>> @@ -708,6 +769,22 @@ static inline void rte_pktmbuf_free(struct rte_mbuf
>>>>> *m)
>>>>>     }
>>>>> }
>>>>> 
>>>>> +/**
>>>>> + * Free a list of packet mbufs back into its original mempool.
>>>>> + *
>>>>> + * Free a list of mbufs by calling rte_pktmbuf_free() in a loop as a wrapper
>>>>> function.
>>>>> + *
>>>>> + * @param m_list
>>>>> + *   An array of rte_mbuf pointers to be freed.
>>>>> + * @param npkts
>>>>> + *   Number of packets to free in list.
>>>>> + */
>>>>> +static inline void rte_pktmbuf_free_bulk(struct rte_mbuf *m_list[], int16_t
>>>>> npkts)
>>>>> +{
>>>>> +     while(npkts--)
>>>>> +             rte_pktmbuf_free(*m_list++);
>>>>> +}
>>>>> +
>>>>> #ifdef RTE_MBUF_REFCNT
>>>>> 
>>>>> /**
>>>>> --
>>>>> 2.1.0
>>>> 
>>> 
>>> Keith Wiles, Principal Technologist with CTO office, Wind River mobile 972-213-5533

Keith Wiles, Principal Technologist with CTO office, Wind River mobile 972-213-5533



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