[dpdk-dev] kni: use bulk functions to allocate and free mbufs
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On Wed, 11 Jan 2017 18:41:28 +0000
Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> On 1/11/2017 6:25 PM, Ananyev, Konstantin wrote:
> >
> >
> >> -----Original Message-----
> >> From: Yigit, Ferruh
> >> Sent: Wednesday, January 11, 2017 5:48 PM
> >> To: Ananyev, Konstantin <konstantin.ananyev@intel.com>; Stephen Hemminger <stephen@networkplumber.org>
> >> Cc: Sergey Vyazmitinov <s.vyazmitinov@brain4net.com>; olivier.matz@6wind.com; dev@dpdk.org
> >> Subject: Re: [dpdk-dev] [PATCH] kni: use bulk functions to allocate and free mbufs
> >>
> >> On 1/11/2017 5:43 PM, Ananyev, Konstantin wrote:
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> >>>> Sent: Wednesday, January 11, 2017 5:36 PM
> >>>> To: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> >>>> Cc: Sergey Vyazmitinov <s.vyazmitinov@brain4net.com>; olivier.matz@6wind.com; Yigit, Ferruh <ferruh.yigit@intel.com>;
> >> dev@dpdk.org
> >>>> Subject: Re: [dpdk-dev] [PATCH] kni: use bulk functions to allocate and free mbufs
> >>>>
> >>>> On Wed, 11 Jan 2017 17:28:21 +0000
> >>>> "Ananyev, Konstantin" <konstantin.ananyev@intel.com> wrote:
> >>>>
> >>>>>> -----Original Message-----
> >>>>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
> >>>>>> Sent: Wednesday, January 11, 2017 4:18 PM
> >>>>>> To: Sergey Vyazmitinov <s.vyazmitinov@brain4net.com>
> >>>>>> Cc: olivier.matz@6wind.com; Yigit, Ferruh <ferruh.yigit@intel.com>; dev@dpdk.org
> >>>>>> Subject: Re: [dpdk-dev] [PATCH] kni: use bulk functions to allocate and free mbufs
> >>>>>>
> >>>>>> On Fri, 30 Dec 2016 04:50:16 +0700
> >>>>>> Sergey Vyazmitinov <s.vyazmitinov@brain4net.com> wrote:
> >>>>>>
> >>>>>>> /**
> >>>>>>> + * Free n packets mbuf back into its original mempool.
> >>>>>>> + *
> >>>>>>> + * Free each mbuf, and all its segments in case of chained buffers. Each
> >>>>>>> + * segment is added back into its original mempool.
> >>>>>>> + *
> >>>>>>> + * @param mp
> >>>>>>> + * The packets mempool.
> >>>>>>> + * @param mbufs
> >>>>>>> + * The packets mbufs array to be freed.
> >>>>>>> + * @param n
> >>>>>>> + * Number of packets.
> >>>>>>> + */
> >>>>>>> +static inline void rte_pktmbuf_free_bulk(struct rte_mempool *mp,
> >>>>>>> + struct rte_mbuf **mbufs, unsigned n)
> >>>>>>> +{
> >>>>>>> + struct rte_mbuf *mbuf, *m_next;
> >>>>>>> + unsigned i;
> >>>>>>> + for (i = 0; i < n; ++i) {
> >>>>>>> + mbuf = mbufs[i];
> >>>>>>> + __rte_mbuf_sanity_check(mbuf, 1);
> >>>>>>> +
> >>>>>>> + mbuf = mbuf->next;
> >>>>>>> + while (mbuf != NULL) {
> >>>>>>> + m_next = mbuf->next;
> >>>>>>> + rte_pktmbuf_free_seg(mbuf);
> >>>>>>> + mbuf = m_next;
> >>>>>>> + }
> >>>>>>> + }
> >>>>>>> + rte_mempool_put_bulk(mp, (void * const *)mbufs, n);
> >>>>>>> +}
> >>>>>>
> >>>>>> The mbufs may come from different pools. You need to handle that.
> >>>>>
> >>>>> I suppose both stituations are possible:
> >>>>> 1) user knows off-hand that all mbufs in the group are from the same mempool
> >>>>> 2) user can't guarantee that all mbufs in the group are from same mempool.
> >>>>>
> >>>>> As I understand that patch is for case 1) only.
> >>>>> For 2) it could be a separate function and separate patch.
> >>>>>
> >>>>> Konstantin
> >>>>>
> >>>>>
> >>>>
> >>>> Please don't make unnecessary assumptions in pursuit of minor optimizations.
> >>>
> >>> I don't suggest to make *any* assumptions.
> >>> What I am saying we can have 2 functions for two different cases.
> >>
> >> kni_free_mbufs() is static function. Even user knows if all mbufs are
> >> some same pool or not, can't pass this information to the free function.
> >>
> >> Of course this information can be passed via new API, or as an update to
> >> exiting API, but I think it is better to update free function to cover
> >> both cases instead of getting this information from user.
> >
> > I suppose misunderstanding came from the fact that kni_free_mbufs()
> > is modified to use rte_pktmbuf_free_bulk(mp, mbufs, n).
> > I am not talking about kni part of the patch
> > (to be honest I didn't pay much attention to it).
> > What I am saying there are many situations when user knows off-hand
> > that all mbufs in that group are from the same mempool and such
> > function will be useful too.
>
> > BTW, for my own curiosity, how it could happen with KNI that
> > kni_fifo_get() would return mbufs not from kni->pktmbuf_pool
> > (I am not really familiar with KNI and its use-cases)?
>
> It gets packets from free queue:
> kni_fifo_get(kni->free_q, ...)
>
> DPDK app may send a mbuf (from any pool, like another port's mempool) to
> kernel, kernel puts buf back to kni->free_q when done with it.
>
> > Konstantin
> >
> >>
> >>> Obviously we'll have to document it properly.
> >>> Konstantin
> >>>
> >>>> It is trivial to write a correct free bulk that handles pool changing.
> >>>> Also the free_seg could be bulked as well.
> >
>
Please write generic code. Something like the following (untested).
This handles multiple pools and multi-segment and indirect mbufs.
Comments
On Wed, Jan 11, 2017 at 10:56:20AM -0800, Stephen Hemminger wrote:
> Please write generic code. Something like the following (untested).
Despite there are few compile errors (which are easy to fix), it works
fine.
More importantly, it saves near 2000 cycles if I apply the bulk free
to virtio_xmit_cleanup(). Only one mp is being used.
--yliu
>
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 4476d75379fd..b7a743ec5c87 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -306,6 +306,9 @@ extern "C" {
> /** Alignment constraint of mbuf private area. */
> #define RTE_MBUF_PRIV_ALIGN 8
>
> +/** Maximum number of mbufs freed in bulk. */
> +#define RTE_MBUF_BULK_FREE 64
> +
> /**
> * Get the name of a RX offload flag
> *
> @@ -1261,6 +1264,50 @@ static inline void rte_pktmbuf_free(struct rte_mbuf *m)
> }
>
> /**
> + * Free n packets mbuf back into its original mempool.
> + *
> + * Free each mbuf, and all its segments in case of chained buffers. Each
> + * segment is added back into its original mempool.
> + *
> + * @param mbufs
> + * The packets mbufs array to be freed.
> + * @param n
> + * Number of packets.
> + */
> +static inline void rte_pktmbuf_free_bulk(struct rte_mbuf **mbufs,
> + unsigned n)
> +{
> + struct rte_mbuf *tofree[RTE_MBUF_BULK_FREE];
> + struct rte_mempool *mp;
> + unsigned i, count = 0;
> +
> + for (i = 0; i < n; i++) {
> + struct rte_mbuf *m, *m_next;
> +
> + for (m = mbufs[i]; m; m = m_next) {
> + m_next = m->next;
> +
> + if (count > 0 &&
> + (unlikely(m->pool != mp || count == RTE_MBUF_BULK_FREE))) {
> + rte_mempool_put_bulk(mp, tofree, count);
> + count = 0;
> + }
> +
> + mp = m->pool;
> +
> + if (likely(__rte_pktmbuf_prefree_seg(m))) {
> + m->next = NULL;
> + tofree[count++] = m;
> + }
> + }
> + }
> +
> + if (likely(count > 0))
> + rte_mempool_put_bulk(mp, tofree, count);
> +}
> +
> +
> +/**
> * Creates a "clone" of the given packet mbuf.
> *
> * Walks through all segments of the given packet mbuf, and for each of them:
>
>
> This handles multiple pools and multi-segment and indirect mbufs.
>
@@ -306,6 +306,9 @@ extern "C" {
/** Alignment constraint of mbuf private area. */
#define RTE_MBUF_PRIV_ALIGN 8
+/** Maximum number of mbufs freed in bulk. */
+#define RTE_MBUF_BULK_FREE 64
+
/**
* Get the name of a RX offload flag
*
@@ -1261,6 +1264,50 @@ static inline void rte_pktmbuf_free(struct rte_mbuf *m)
}
/**
+ * Free n packets mbuf back into its original mempool.
+ *
+ * Free each mbuf, and all its segments in case of chained buffers. Each
+ * segment is added back into its original mempool.
+ *
+ * @param mbufs
+ * The packets mbufs array to be freed.
+ * @param n
+ * Number of packets.
+ */
+static inline void rte_pktmbuf_free_bulk(struct rte_mbuf **mbufs,
+ unsigned n)
+{
+ struct rte_mbuf *tofree[RTE_MBUF_BULK_FREE];
+ struct rte_mempool *mp;
+ unsigned i, count = 0;
+
+ for (i = 0; i < n; i++) {
+ struct rte_mbuf *m, *m_next;
+
+ for (m = mbufs[i]; m; m = m_next) {
+ m_next = m->next;
+
+ if (count > 0 &&
+ (unlikely(m->pool != mp || count == RTE_MBUF_BULK_FREE))) {
+ rte_mempool_put_bulk(mp, tofree, count);
+ count = 0;
+ }
+
+ mp = m->pool;
+
+ if (likely(__rte_pktmbuf_prefree_seg(m))) {
+ m->next = NULL;
+ tofree[count++] = m;
+ }
+ }
+ }
+
+ if (likely(count > 0))
+ rte_mempool_put_bulk(mp, tofree, count);
+}
+
+
+/**
* Creates a "clone" of the given packet mbuf.
*
* Walks through all segments of the given packet mbuf, and for each of them: