patches for DPDK stable branches
 help / color / Atom feed
From: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
To: dev@dpdk.org, honnappa.nagarahalli@arm.com, phil.yang@arm.com,
	jgrajcia@cisco.com, ferruh.yigit@intel.com
Cc: nd@arm.com, stable@dpdk.org
Subject: [dpdk-stable] [PATCH 1/4] net/memif: do not update local copy of tail in tx function
Date: Mon, 21 Sep 2020 14:22:51 -0500
Message-ID: <20200921192254.20560-1-honnappa.nagarahalli@arm.com> (raw)

In the case of S2M queues, the receiver synchronizes with the sender
(i.e. informs of the packets it has received) using ring->tail.
Hence, the sender does not need to update last_tail.

In the case of M2S queues, the receiver uses last_tail to
keep track of the descriptors it has received. The
sender is not required to update the last_tail. Updating
the last_tail makes it a shared variable between the
transmitter and receiver affecting the performance.

Fixes: 09c7e63a71f9 ("net/memif: introduce memory interface PMD")
Cc: jgrajcia@cisco.com
Cc: stable@dpdk.org

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
---
 drivers/net/memif/rte_eth_memif.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/memif/rte_eth_memif.c b/drivers/net/memif/rte_eth_memif.c
index c1c7e9f8d..fd7dbc53e 100644
--- a/drivers/net/memif/rte_eth_memif.c
+++ b/drivers/net/memif/rte_eth_memif.c
@@ -568,12 +568,10 @@ eth_memif_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	ring_size = 1 << mq->log2_ring_size;
 	mask = ring_size - 1;
 
-	n_free = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE) - mq->last_tail;
-	mq->last_tail += n_free;
-
 	if (type == MEMIF_RING_S2M) {
 		slot = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE);
-		n_free = ring_size - slot + mq->last_tail;
+		n_free = ring_size - slot +
+				__atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
 	} else {
 		slot = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
 		n_free = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE) - slot;
-- 
2.17.1


             reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-21 19:22 Honnappa Nagarahalli [this message]
2020-09-21 19:22 ` [dpdk-stable] [PATCH 2/4] net/memif: relax the load of ring tail pointer for M2S ring Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-stable] [PATCH 3/4] net/memif: relax the load of ring head pointer for S2M ring Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-stable] [PATCH 4/4] net/memif: relax the load of ring head pointer for M2S ring Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-stable] [PATCH v2 1/8] net/memif: do not update local copy of tail in tx function Honnappa Nagarahalli
2020-09-28 19:03   ` [dpdk-stable] [PATCH v2 2/8] net/memif: relax the load of ring tail pointer for M2S ring Honnappa Nagarahalli
2020-09-28 19:03   ` [dpdk-stable] [PATCH v2 3/8] net/memif: relax the load of ring head " Honnappa Nagarahalli
2020-09-28 19:03   ` [dpdk-stable] [PATCH v2 4/8] net/memif: relax the load of ring head pointer for S2M ring Honnappa Nagarahalli
2020-09-28 20:53   ` [dpdk-stable] [dpdk-dev] [PATCH v2 1/8] net/memif: do not update local copy of tail in tx function Stephen Hemminger
2020-09-29  5:24     ` Honnappa Nagarahalli
2020-10-07 17:08   ` [dpdk-stable] " Honnappa Nagarahalli
2020-10-09 11:23     ` Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco)
2020-10-09 15:59       ` Ferruh Yigit

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200921192254.20560-1-honnappa.nagarahalli@arm.com \
    --to=honnappa.nagarahalli@arm.com \
    --cc=dev@dpdk.org \
    --cc=ferruh.yigit@intel.com \
    --cc=jgrajcia@cisco.com \
    --cc=nd@arm.com \
    --cc=phil.yang@arm.com \
    --cc=stable@dpdk.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

patches for DPDK stable branches

Archives are clonable:
	git clone --mirror http://inbox.dpdk.org/stable/0 stable/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 stable stable/ http://inbox.dpdk.org/stable \
		stable@dpdk.org
	public-inbox-index stable


Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.stable


AGPL code for this site: git clone https://public-inbox.org/ public-inbox