[dpdk-dev] [PATCH v2] rte_mbuf: mbuf bulk alloc/free functions added + unittest

[Vadim Suraev]

Hi, Neil

>I think what you need to do here is enhance the underlying pktmbuf
interface
>such that an rte_mbuf structure has a destructor method association with it
>which is called when its refcnt reaches zero.  That way the
>rte_pktmbuf_bulk_free function can just decrement the refcnt on each
>mbuf_structure, and the pool as a whole can be returned when the destructor
>function discovers that all mbufs in that bulk pool are freed.

I thought again and it looks to me that if mempool_cache is enabled,
rte_pktmbuf_bulk_free and  are redundant because the logic would be very
similar to already implemented in rte_mempool. Probably the only
rte_pktmbuf_alloc_bulk makes sense in this patch?

Regards,
 Vadim.

On Wed, Mar 18, 2015 at 10:58 PM, Neil Horman <nhorman at tuxdriver.com> wrote:

> On Wed, Mar 18, 2015 at 10:21:18PM +0200, vadim.suraev at gmail.com wrote:
> > From: "vadim.suraev at gmail.com" <vadim.suraev at gmail.com>
> >
> > This patch adds mbuf bulk allocation/freeing functions and unittest
> >
> > Signed-off-by: Vadim Suraev
> > <vadim.suraev at gmail.com>
> > ---
> > New in v2:
> >     - function rte_pktmbuf_alloc_bulk added
> >     - function rte_pktmbuf_bulk_free added
> >     - function rte_pktmbuf_free_chain added
> >     - applied reviewers' comments
> >
> >  app/test/test_mbuf.c       |   94
> +++++++++++++++++++++++++++++++++++++++++++-
> >  lib/librte_mbuf/rte_mbuf.h |   91
> ++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 184 insertions(+), 1 deletion(-)
> >
> > diff --git a/app/test/test_mbuf.c b/app/test/test_mbuf.c
> > index 1ff66cb..b20c6a4 100644
> > --- a/app/test/test_mbuf.c
> > +++ b/app/test/test_mbuf.c
> > @@ -77,6 +77,7 @@
> >  #define REFCNT_RING_SIZE        (REFCNT_MBUF_NUM * REFCNT_MAX_REF)
> >
> >  #define MAKE_STRING(x)          # x
> > +#define MBUF_POOL_LOCAL_CACHE_SIZE 32
> >
> >  static struct rte_mempool *pktmbuf_pool = NULL;
> >
> > @@ -405,6 +406,84 @@ test_pktmbuf_pool(void)
> >       return ret;
> >  }
> >
> ><snip>
> > diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> > index 17ba791..fabeae2 100644
> > --- a/lib/librte_mbuf/rte_mbuf.h
> > +++ b/lib/librte_mbuf/rte_mbuf.h
> > @@ -825,6 +825,97 @@ static inline void rte_pktmbuf_free(struct rte_mbuf
> *m)
> >  }
> >
> >  /**
> > + * Allocate a bulk of mbufs, initiate refcnt and resets
> > + *
> > + * @param pool
> > + *    memory pool to allocate from
> > + * @param mbufs
> > + *    Array of pointers to mbuf
> > + * @param count
> > + *    Array size
> > + */
> > +static inline int rte_pktmbuf_alloc_bulk(struct rte_mempool *pool,
> > +                                      struct rte_mbuf **mbufs,
> > +                                      unsigned count)
> > +{
> > +     unsigned idx;
> > +     int rc = 0;
> > +
> > +     rc = rte_mempool_get_bulk(pool, (void **)mbufs, count);
> > +     if (unlikely(rc))
> > +             return rc;
> > +
> > +     for (idx = 0; idx < count; idx++) {
> > +             RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
> > +             rte_mbuf_refcnt_set(mbufs[idx], 1);
> > +             rte_pktmbuf_reset(mbufs[idx]);
> > +     }
> > +     return rc;
> > +}
> > +
> > +/**
> > + * Free a bulk of mbufs into its original mempool.
> > + * This function assumes:
> > + * - refcnt equals 1
> > + * - mbufs are direct
> > + * - all mbufs must belong to the same mempool
> > + *
> > + * @param mbufs
> > + *    Array of pointers to mbuf
> > + * @param count
> > + *    Array size
> > + */
> > +static inline void rte_pktmbuf_bulk_free(struct rte_mbuf **mbufs,
> > +                                      unsigned count)
> > +{
> > +     unsigned idx;
> > +
> > +     RTE_MBUF_ASSERT(count > 0);
> > +
> > +     for (idx = 0; idx < count; idx++) {
> > +             RTE_MBUF_ASSERT(mbufs[idx]->pool == mbufs[0]->pool);
> > +             RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 1);
> > +             rte_mbuf_refcnt_set(mbufs[idx], 0);
> This is really a misuse of the API.  The entire point of reference
> counting is
> to know when an mbuf has no more references and can be freed.  By forcing
> all
> the reference counts to zero here, you allow the refcnt infrastructure to
> be
> circumvented, causing memory leaks.
>
> I think what you need to do here is enhance the underlying pktmbuf
> interface
> such that an rte_mbuf structure has a destructor method association with it
> which is called when its refcnt reaches zero.  That way the
> rte_pktmbuf_bulk_free function can just decrement the refcnt on each
> mbuf_structure, and the pool as a whole can be returned when the destructor
> function discovers that all mbufs in that bulk pool are freed.
>
> Neil
>
>