[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 22:07:56 CEST 2014


Attaching to the list does not work. If you want the code let me know it is only about 5K in size.

On Oct 6, 2014, at 2:45 PM, Wiles, Roger Keith <keith.wiles at windriver.com> wrote:

> 
> On Oct 6, 2014, at 11:13 AM, Wiles, Roger Keith <keith.wiles at windriver.com> wrote:
> 
>> 
>> 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.
> 
> I compared the clang assembler (.s file) output from an example test code I wrote to see if we have any differences in the code using the two styles and I found no difference and the code looked the same. I am not a Intel assembler expert and I would suggest someone else determine if it generates different code. I tried to compare the GCC outputs and it did look the same to me.
> 
> I have attached the code and output, please let me know if I did something wrong, but as it stands using the original style is what I want to go with.
> 
>>> 
>>> 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
> 
> 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



More information about the dev mailing list