diff mbox series

[v3,1/2] net/mlx5: optimize inline mbuf freeing

Message ID 1611335529-26503-2-git-send-email-viacheslavo@nvidia.com (mailing list archive)
State Accepted, archived
Delegated to: Raslan Darawsheh
Headers show
Series add mbuf fast free offload support | expand

Checks

Context Check Description
ci/checkpatch success coding style OK

Commit Message

Slava Ovsiienko Jan. 22, 2021, 5:12 p.m. UTC
The mlx5 PMD supports packet data inlining by pushing data
to the transmit descriptor. If packet is short enough and all
data are inline, the mbuf is not needed for data send anymore
and can be freed.

The mbuf free was performed in the most inner loop building
the transmit descriptors. This patch postpones the mbuf free
transaction to the tx_burst routine exit, optimizing the loop
and allowing the bulk freeing for the multiple mbufs in single
pool API call.

Cc: stable@dpdk.org

Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
---
 drivers/net/mlx5/mlx5_rxtx.c | 38 ++++++++++++++++++++++++++++++++++----
 drivers/net/mlx5/mlx5_rxtx.h |  1 +
 2 files changed, 35 insertions(+), 4 deletions(-)

Comments

Ferruh Yigit Jan. 27, 2021, 12:44 p.m. UTC | #1
On 1/22/2021 5:12 PM, Viacheslav Ovsiienko wrote:
> The mlx5 PMD supports packet data inlining by pushing data
> to the transmit descriptor. If packet is short enough and all
> data are inline, the mbuf is not needed for data send anymore
> and can be freed.
> 
> The mbuf free was performed in the most inner loop building
> the transmit descriptors. This patch postpones the mbuf free
> transaction to the tx_burst routine exit, optimizing the loop
> and allowing the bulk freeing for the multiple mbufs in single
> pool API call.
> 
> Cc: stable@dpdk.org
> 

Hi Slava,

This patch is optimization for inline mbufs, right, it is not a fix, should it 
be backported?

cc'ed LTS maintainers.

I am dropping the stable to for now in the next-net, can add it later based on 
discussion result.

> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
Ferruh Yigit Jan. 27, 2021, 12:48 p.m. UTC | #2
On 1/27/2021 12:44 PM, Ferruh Yigit wrote:
> On 1/22/2021 5:12 PM, Viacheslav Ovsiienko wrote:
>> The mlx5 PMD supports packet data inlining by pushing data
>> to the transmit descriptor. If packet is short enough and all
>> data are inline, the mbuf is not needed for data send anymore
>> and can be freed.
>>
>> The mbuf free was performed in the most inner loop building
>> the transmit descriptors. This patch postpones the mbuf free
>> transaction to the tx_burst routine exit, optimizing the loop
>> and allowing the bulk freeing for the multiple mbufs in single
>> pool API call.
>>
>> Cc: stable@dpdk.org
>>
> 
> Hi Slava,
> 
> This patch is optimization for inline mbufs, right, it is not a fix, should it 
> be backported?
> 
> cc'ed LTS maintainers.
> 

cc'ed now.

> I am dropping the stable to for now in the next-net, can add it later based on 
> discussion result.
> 
>> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
>
Slava Ovsiienko Jan. 28, 2021, 9:14 a.m. UTC | #3
Hi, Ferruh

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Wednesday, January 27, 2021 14:45
> To: Slava Ovsiienko <viacheslavo@nvidia.com>; dev@dpdk.org
> Cc: Raslan Darawsheh <rasland@nvidia.com>; Matan Azrad
> <matan@nvidia.com>; Ori Kam <orika@nvidia.com>; NBU-Contact-Thomas
> Monjalon <thomas@monjalon.net>; Alexander Kozyrev
> <akozyrev@nvidia.com>; stable@dpdk.org
> Subject: Re: [dpdk-stable] [PATCH v3 1/2] net/mlx5: optimize inline mbuf
> freeing
> 
> On 1/22/2021 5:12 PM, Viacheslav Ovsiienko wrote:
> > The mlx5 PMD supports packet data inlining by pushing data to the
> > transmit descriptor. If packet is short enough and all data are
> > inline, the mbuf is not needed for data send anymore and can be freed.
> >
> > The mbuf free was performed in the most inner loop building the
> > transmit descriptors. This patch postpones the mbuf free transaction
> > to the tx_burst routine exit, optimizing the loop and allowing the
> > bulk freeing for the multiple mbufs in single pool API call.
> >
> > Cc: stable@dpdk.org
> >
> 
> Hi Slava,
> 
> This patch is optimization for inline mbufs, right, it is not a fix, should it be
> backported?
Not critical, but nice to have this small optimization in LTS.

> 
> cc'ed LTS maintainers.
> 
> I am dropping the stable to for now in the next-net, can add it later based on
> discussion result.

OK, let's consider this backporting in dedicated way, thank you.

With best regards, Slava
Thomas Monjalon Jan. 28, 2021, 9:34 a.m. UTC | #4
28/01/2021 10:14, Slava Ovsiienko:
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> > On 1/22/2021 5:12 PM, Viacheslav Ovsiienko wrote:
> > > The mlx5 PMD supports packet data inlining by pushing data to the
> > > transmit descriptor. If packet is short enough and all data are
> > > inline, the mbuf is not needed for data send anymore and can be freed.
> > >
> > > The mbuf free was performed in the most inner loop building the
> > > transmit descriptors. This patch postpones the mbuf free transaction
> > > to the tx_burst routine exit, optimizing the loop and allowing the
> > > bulk freeing for the multiple mbufs in single pool API call.
> > >
> > > Cc: stable@dpdk.org
> > >
> > 
> > Hi Slava,
> > 
> > This patch is optimization for inline mbufs, right, it is not a fix, should it be
> > backported?
> Not critical, but nice to have this small optimization in LTS.
> 
> > 
> > cc'ed LTS maintainers.
> > 
> > I am dropping the stable to for now in the next-net, can add it later based on
> > discussion result.
> 
> OK, let's consider this backporting in dedicated way, thank you.

Consensus from techboard is to reject optimizations in LTS for now.
Some acceptance guidelines will be written soon.
Not sure this one will be considered.
diff mbox series

Patch

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 3497765..97912dd 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -1990,6 +1990,17 @@  enum mlx5_txcmp_code {
 		}
 	}
 }
+/*
+ * No inline version to free buffers for optimal call
+ * on the tx_burst completion.
+ */
+static __rte_noinline void
+__mlx5_tx_free_mbuf(struct rte_mbuf **__rte_restrict pkts,
+		    unsigned int pkts_n,
+		    unsigned int olx __rte_unused)
+{
+	mlx5_tx_free_mbuf(pkts, pkts_n, olx);
+}
 
 /**
  * Free the mbuf from the elts ring buffer till new tail.
@@ -4408,10 +4419,25 @@  enum mlx5_txcmp_code {
 			MLX5_ASSERT(room >= tlen);
 			room -= tlen;
 			/*
-			 * Packet data are completely inlined,
-			 * free the packet immediately.
+			 * Packet data are completely inline,
+			 * we can try to free the packet.
+			 */
+			if (likely(loc->pkts_sent == loc->mbuf_free)) {
+				/*
+				 * All the packets from the burst beginning
+				 * are inline, we can free mbufs directly
+				 * from the origin array on tx_burst exit().
+				 */
+				loc->mbuf_free++;
+				goto next_mbuf;
+			}
+			/*
+			 * In order no to call rte_pktmbuf_free_seg() here,
+			 * in the most inner loop (that might be very
+			 * expensive) we just save the mbuf in elts.
 			 */
-			rte_pktmbuf_free_seg(loc->mbuf);
+			txq->elts[txq->elts_head++ & txq->elts_m] = loc->mbuf;
+			loc->elts_free--;
 			goto next_mbuf;
 pointer_empw:
 			/*
@@ -4433,6 +4459,7 @@  enum mlx5_txcmp_code {
 			mlx5_tx_dseg_ptr(txq, loc, dseg, dptr, dlen, olx);
 			/* We have to store mbuf in elts.*/
 			txq->elts[txq->elts_head++ & txq->elts_m] = loc->mbuf;
+			loc->elts_free--;
 			room -= MLX5_WQE_DSEG_SIZE;
 			/* Ring buffer wraparound is checked at the loop end.*/
 			++dseg;
@@ -4442,7 +4469,6 @@  enum mlx5_txcmp_code {
 			slen += dlen;
 #endif
 			loc->pkts_sent++;
-			loc->elts_free--;
 			pkts_n--;
 			if (unlikely(!pkts_n || !loc->elts_free)) {
 				/*
@@ -4892,6 +4918,8 @@  enum mlx5_txcmp_code {
 	MLX5_ASSERT(txq->wqe_s >= (uint16_t)(txq->wqe_ci - txq->wqe_pi));
 	if (unlikely(!pkts_n))
 		return 0;
+	if (MLX5_TXOFF_CONFIG(INLINE))
+		loc.mbuf_free = 0;
 	loc.pkts_sent = 0;
 	loc.pkts_copy = 0;
 	loc.wqe_last = NULL;
@@ -5155,6 +5183,8 @@  enum mlx5_txcmp_code {
 	/* Increment sent packets counter. */
 	txq->stats.opackets += loc.pkts_sent;
 #endif
+	if (MLX5_TXOFF_CONFIG(INLINE) && loc.mbuf_free)
+		__mlx5_tx_free_mbuf(pkts, loc.mbuf_free, olx);
 	return loc.pkts_sent;
 }
 
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index 7756ed3..9dac408 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -209,6 +209,7 @@  struct mlx5_txq_local {
 	uint16_t wqe_free; /* available wqe remain. */
 	uint16_t mbuf_off; /* data offset in current mbuf. */
 	uint16_t mbuf_nseg; /* number of remaining mbuf. */
+	uint16_t mbuf_free; /* number of inline mbufs to free. */
 };
 
 /* TX queue descriptor. */