> -----Original Message----- > From: Wiles, Roger Keith [mailto:keith.wiles at windriver.com] > Sent: Monday, October 06, 2014 9:08 PM > To: Ananyev, Konstantin > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH 2/2] Adding the routines > rte_pktmbuf_alloc_bulk() and rte_pktmbuf_free_bulk() > > 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.
That's was my question: Modern compilers are able to generate a good code for a simple loop as above. So what's the point to use 2 iterators inside the loop, when just one is enough? Nothing wrong technically, but makes code a bit harder to follow. Plus, in general, it is a good practise to minimise number of iterators inside the loop, when possible. Konstantin > > > > 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 >
