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

Ananyev, Konstantin konstantin.ananyev at intel.com
Mon Oct 6 17:54:38 CEST 2014


> 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

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. 

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]);

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
> >


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