From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ophir Munk Subject: Re: [PATCH v2 2/7] net/mlx4: inline more Tx functions Date: Thu, 26 Oct 2017 14:27:34 +0000 Message-ID: References: <1508752838-30408-1-git-send-email-ophirmu@mellanox.com> <1508768520-4810-1-git-send-email-ophirmu@mellanox.com> <1508768520-4810-3-git-send-email-ophirmu@mellanox.com> <20171025164938.GH26782@6wind.com> <20171026074853.GL26782@6wind.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: "dev@dpdk.org" , Thomas Monjalon , "Olga Shern" , Matan Azrad To: Adrien Mazarguil Return-path: Received: from EUR02-AM5-obe.outbound.protection.outlook.com (mail-eopbgr00047.outbound.protection.outlook.com [40.107.0.47]) by dpdk.org (Postfix) with ESMTP id E851E1AEE9 for ; Thu, 26 Oct 2017 16:27:37 +0200 (CEST) In-Reply-To: <20171026074853.GL26782@6wind.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Hi, Please see inside On Thursday, October 26, 2017 10:49 AM Adrien Mazarguil wrote: > To: Ophir Munk > Cc: dev@dpdk.org; Thomas Monjalon ; Olga Shern > ; Matan Azrad > Subject: Re: [PATCH v2 2/7] net/mlx4: inline more Tx functions >=20 > Hi Ophir, >=20 > Please see below. >=20 > On Wed, Oct 25, 2017 at 09:42:46PM +0000, Ophir Munk wrote: > > Hi Adrien, > > > > On Wednesday, October 25, 2017 7:50 PM, Adrien Mazarguil wrote: > > > > > > Hi Ophir, > > > > > > On Mon, Oct 23, 2017 at 02:21:55PM +0000, Ophir Munk wrote: > > > > Change functions to inline on Tx fast path to improve performance > > > > > > > > Inside the inline function call other functions to handle "unlikely= " > > > > cases such that the inline function code footprint is small. > > > > > > > > Signed-off-by: Ophir Munk > > > > > > Reading this, it's like adding __rte_always_inline improves > > > performance at all, which I doubt unless you can show proof through > performance results. > > > > > > When in doubt, leave it to the compiler, the static keyword is > > > usually enough of a hint. Too much forced inlining may actually be > harmful. > > > > > > What this patch really does is splitting the heavy > > > lookup/registration function in two halves with one small static > > > inline function for the lookup part that calls the separate > > > registration part in the unlikely event MR is not already registered. > > > > > > Thankfully the compiler doesn't inline the large registration > > > function back, which results in the perceived performance > > > improvement for the time being, however there is no guarantee it > > > won't happen in the future (you didn't use the noinline keyword on th= e > registration function for that). > > > > > > Therefore I have a bunch of comments and suggestions, see below. > > > > > > > --- > > > > drivers/net/mlx4/mlx4_rxtx.c | 43 > > > > ++++++------------------------------ > > > > drivers/net/mlx4/mlx4_rxtx.h | 52 > > > > +++++++++++++++++++++++++++++++++++++++++++- > > > > 2 files changed, 58 insertions(+), 37 deletions(-) > > > > > > > > diff --git a/drivers/net/mlx4/mlx4_rxtx.c > > > > b/drivers/net/mlx4/mlx4_rxtx.c index 011ea79..ae37f9b 100644 > > > > --- a/drivers/net/mlx4/mlx4_rxtx.c > > > > +++ b/drivers/net/mlx4/mlx4_rxtx.c > > > > @@ -220,54 +220,25 @@ mlx4_txq_complete(struct txq *txq) > > > > return 0; > > > > } > > > > > > > > -/** > > > > - * Get memory pool (MP) from mbuf. If mbuf is indirect, the pool > > > > from which > > > > - * the cloned mbuf is allocated is returned instead. > > > > - * > > > > - * @param buf > > > > - * Pointer to mbuf. > > > > - * > > > > - * @return > > > > - * Memory pool where data is located for given mbuf. > > > > - */ > > > > -static struct rte_mempool * > > > > -mlx4_txq_mb2mp(struct rte_mbuf *buf) -{ > > > > - if (unlikely(RTE_MBUF_INDIRECT(buf))) > > > > - return rte_mbuf_from_indirect(buf)->pool; > > > > - return buf->pool; > > > > -} > > > > > > > > /** > > > > - * Get memory region (MR) <-> memory pool (MP) association from > > > >txq- mp2mr[]. > > > > - * Add MP to txq->mp2mr[] if it's not registered yet. If mp2mr[] > > > >is full, > > > > - * remove an entry first. > > > > + * Add memory region (MR) <-> memory pool (MP) association to > > > > + txq- > > > >mp2mr[]. > > > > + * If mp2mr[] is full, remove an entry first. > > > > * > > > > * @param txq > > > > * Pointer to Tx queue structure. > > > > * @param[in] mp > > > > - * Memory pool for which a memory region lkey must be returned. > > > > + * Memory pool for which a memory region lkey must be added > > > > + * @param[in] i > > > > + * Index in memory pool (MP) where to add memory region (MR) > > > > * > > > > * @return > > > > - * mr->lkey on success, (uint32_t)-1 on failure. > > > > + * Added mr->lkey on success, (uint32_t)-1 on failure. > > > > */ > > > > -uint32_t > > > > -mlx4_txq_mp2mr(struct txq *txq, struct rte_mempool *mp) > > > > +uint32_t mlx4_txq_add_mr(struct txq *txq, struct rte_mempool *mp, > > > > +uint32_t i) > > > > { > > > > - unsigned int i; > > > > struct ibv_mr *mr; > > > > > > > > - for (i =3D 0; (i !=3D RTE_DIM(txq->mp2mr)); ++i) { > > > > - if (unlikely(txq->mp2mr[i].mp =3D=3D NULL)) { > > > > - /* Unknown MP, add a new MR for it. */ > > > > - break; > > > > - } > > > > - if (txq->mp2mr[i].mp =3D=3D mp) { > > > > - assert(txq->mp2mr[i].lkey !=3D (uint32_t)-1); > > > > - assert(txq->mp2mr[i].mr->lkey =3D=3D txq- > > > >mp2mr[i].lkey); > > > > - return txq->mp2mr[i].lkey; > > > > - } > > > > - } > > > > /* Add a new entry, register MR first. */ > > > > DEBUG("%p: discovered new memory pool \"%s\" (%p)", > > > > (void *)txq, mp->name, (void *)mp); diff --git > > > >a/drivers/net/mlx4/mlx4_rxtx.h b/drivers/net/mlx4/mlx4_rxtx.h index > > > > e10bbca..719ef45 100644 > > > > --- a/drivers/net/mlx4/mlx4_rxtx.h > > > > +++ b/drivers/net/mlx4/mlx4_rxtx.h > > > > @@ -53,6 +53,7 @@ > > > > > > > > #include "mlx4.h" > > > > #include "mlx4_prm.h" > > > > +#include "mlx4_utils.h" > > > > > > Why? > > > > > > > > > > > /** Rx queue counters. */ > > > > struct mlx4_rxq_stats { > > > > @@ -160,7 +161,6 @@ void mlx4_rx_queue_release(void *dpdk_rxq); > > > > > > > > /* mlx4_rxtx.c */ > > > > > > > > -uint32_t mlx4_txq_mp2mr(struct txq *txq, struct rte_mempool *mp); > > > > uint16_t mlx4_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, > > > > uint16_t pkts_n); > > > > uint16_t mlx4_rx_burst(void *dpdk_rxq, struct rte_mbuf **pkts, @@ > > > > -169,6 +169,8 @@ uint16_t mlx4_tx_burst_removed(void *dpdk_txq, > > > struct rte_mbuf **pkts, > > > > uint16_t pkts_n); > > > > uint16_t mlx4_rx_burst_removed(void *dpdk_rxq, struct rte_mbuf > **pkts, > > > > uint16_t pkts_n); > > > > +uint32_t mlx4_txq_add_mr(struct txq *txq, struct rte_mempool *mp, > > > > + unsigned int i); > > > > > > > > /* mlx4_txq.c */ > > > > > > > > @@ -177,4 +179,52 @@ int mlx4_tx_queue_setup(struct rte_eth_dev > > > *dev, uint16_t idx, > > > > const struct rte_eth_txconf *conf); void > > > > mlx4_tx_queue_release(void *dpdk_txq); > > > > > > > > +/** > > > > + * Get memory pool (MP) from mbuf. If mbuf is indirect, the pool > > > > +from which > > > > + * the cloned mbuf is allocated is returned instead. > > > > + * > > > > + * @param buf > > > > + * Pointer to mbuf. > > > > + * > > > > + * @return > > > > + * Memory pool where data is located for given mbuf. > > > > + */ > > > > +static __rte_always_inline struct rte_mempool * > > > > +mlx4_txq_mb2mp(struct rte_mbuf *buf) { > > > > + if (unlikely(RTE_MBUF_INDIRECT(buf))) > > > > + return rte_mbuf_from_indirect(buf)->pool; > > > > + return buf->pool; > > > > +} > > > > + > > > > +/** > > > > + * Get memory region (MR) <-> memory pool (MP) association from > > > > +txq- > > > >mp2mr[]. > > > > + * Call mlx4_txq_add_mr() if MP is not registered yet. > > > > + * > > > > + * @param txq > > > > + * Pointer to Tx queue structure. > > > > + * @param[in] mp > > > > + * Memory pool for which a memory region lkey must be returned. > > > > + * > > > > + * @return > > > > + * mr->lkey on success, (uint32_t)-1 on failure. > > > > + */ > > > > +static __rte_always_inline uint32_t > > > > > > Note __rte_always_inline is defined in rte_common.h and should be > > > explicitly included (however don't do that, see below). > > > > > > > +mlx4_txq_mp2mr(struct txq *txq, struct rte_mempool *mp) { > > > > + unsigned int i; > > > > + > > > > + for (i =3D 0; (i !=3D RTE_DIM(txq->mp2mr)); ++i) { > > > > + if (unlikely(txq->mp2mr[i].mp =3D=3D NULL)) { > > > > + /* Unknown MP, add a new MR for it. */ > > > > + break; > > > > + } > > > > + if (txq->mp2mr[i].mp =3D=3D mp) { > > > > + assert(txq->mp2mr[i].lkey !=3D (uint32_t)-1); > > > > + assert(txq->mp2mr[i].mr->lkey =3D=3D txq- > > > >mp2mr[i].lkey); > > > > > > assert() requires assert.h (but don't include it, see subsequent > suggestion). > > > > > > > + return txq->mp2mr[i].lkey; > > > > + } > > > > + } > > > > + return mlx4_txq_add_mr(txq, mp, i); } > > > > #endif /* MLX4_RXTX_H_ */ > > > > > > So as described above, these functions do not need the > > > __rte_always_inline, please remove it. They also do not need to be > > > located in a header file; the reason it's the case for their mlx5 > > > counterparts is that they have to be shared between > > > vectorized/non-vectorized code. No such requirement here, you should > move them back to their original spot. > > > > > > > Static function mlx4_txq_mp2mr() must be in a header file because it is > shared by 2 files: mlx4_txq.c and mlx4_rxtx.c. > > It is not related to vectorized/non-vectorized code in mlx5. > > Having said that -__rte_always_inline is required as well otherwise > > compilation fails with > > drivers/net/mlx4/mlx4_rxtx.h:200:1: error: 'mlx4_txq_mp2mr' defined > > but not used [-Werror=3Dunused-function] for files which include > > mlx4_rxtx.h >=20 > All right, then what you were looking or was static inline, not *force* i= nline. > The former is a hint, the latter doesn't leave much of a choice to the > compiler, it means you're sure this way brings the most performance, > however for this patch I really think inlining plays a really minor part = (even > changes anything at all) compared to dividing this function, which is the= real > performance improvement. Without inline I get ~0.2Mpps degradation on my setup, therefore I suggest = keeping inline. The final call is yours. Please let me know if to leave inline or remove. >=20 > > > My suggestion for this performance improvement is to move > > > mlx4_txq_add_mr() to a different file, mlx4_mr.c looks like a good > > > candidate. This fact will ensure it's never inlined and far away > > > from the data path. > > > > > > > Function mlx4_txq_add_mr() is relatively small. > > What do you say about preceding it with __attribute((noinline)) instead= of > creating a new file? >=20 > What I mean is you should declare mlx4_txq_add_mr() which does the heavy > lifting inside mlx4_mr.c and provide its definition in mlx4.h instead of > mlx4_rxtx.h. >=20 > Then, mlx4_txq_mp2mr() can remain defined in mlx4_rxtx.c in its original > spot as a non-static function with its public declaration remaining in > mlx4_rxtx.h for users outside of this file. >=20 That's done before. mlx4_txq_mp2mr() is defined in mlx4_rxtx.c as described= . > The fact mlx4_txq_mp2mr() remains defined in that file *before* > mlx4_post_send()'s definition where it's needed allows the compiler to > optimize it away as if it was static inline thanks to -O3, that is, unles= s it thinks > doing so would hurt performance, but as a (now) small function this > shouldn't be an issue. >=20 > Other reasons includes that doing so would make a smaller diff that focus= es > on the performance improvement itself. The extra performance brought by a > statically inlined version of mlx4_txq_mp2mr() is not needed in mlx4_txq.= c, > whose only purpose is to set up queues. I have moved mlx4_txq_add_mr() to mlx_mr.c. One of the disadvantages of mov= ing it is that now=20 it requires adding #include "mlx4_rxtx.h" in the C file in order to know th= e details of txq struct. I liked mlx4_mr.c for being encapsulated from any Tx/Rx specific structures= and just handling MR issues. >=20 > -- > Adrien Mazarguil > 6WIND