patches for DPDK stable branches
 help / color / mirror / Atom feed
From: Kevin Traynor <ktraynor@redhat.com>
To: Alan Dewar <alan.dewar@att.com>
Cc: Jasvinder Singh <jasvinder.singh@intel.com>,
	dpdk stable <stable@dpdk.org>
Subject: [dpdk-stable] patch 'sched: fix port time rounding' has been queued to LTS release 18.11.10
Date: Fri, 17 Jul 2020 17:32:09 +0100
Message-ID: <20200717163214.4839-21-ktraynor@redhat.com> (raw)
In-Reply-To: <20200717163214.4839-1-ktraynor@redhat.com>

Hi,

FYI, your patch has been queued to LTS release 18.11.10

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 07/23/20. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable-queue/commit/38f30a1f450b56666f5339ee4e68f795cdf51b06

Thanks.

Kevin.

---
From 38f30a1f450b56666f5339ee4e68f795cdf51b06 Mon Sep 17 00:00:00 2001
From: Alan Dewar <alan.dewar@att.com>
Date: Thu, 25 Jun 2020 10:59:30 +0100
Subject: [PATCH] sched: fix port time rounding

[ upstream commit 83415d4fd88c925002655aa755601998a3cdef2c ]

The QoS scheduler works off port time that is computed from the number
of CPU cycles that have elapsed since the last time the port was
polled.   It divides the number of elapsed cycles to calculate how
many bytes can be sent, however this division can generate rounding
errors, where some fraction of a byte sent may be lost.

Lose enough of these fractional bytes and the QoS scheduler
underperforms.  The problem is worse with low bandwidths.

To compensate for this rounding error this fix doesn't advance the
port's time_cpu_cycles by the number of cycles that have elapsed,
but by multiplying the computed number of bytes that can be sent
(which has been rounded down) by number of cycles per byte.
This will mean that port's time_cpu_cycles will lag behind the CPU
cycles momentarily.  At the next poll, the lag will be taken into
account.

Fixes: de3cfa2c98 ("sched: initial import")

Signed-off-by: Alan Dewar <alan.dewar@att.com>
Acked-by: Jasvinder Singh <jasvinder.singh@intel.com>
---
 lib/librte_sched/rte_sched.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/librte_sched/rte_sched.c b/lib/librte_sched/rte_sched.c
index 89c3d1e7f7..d8ace20fe0 100644
--- a/lib/librte_sched/rte_sched.c
+++ b/lib/librte_sched/rte_sched.c
@@ -201,4 +201,5 @@ struct rte_sched_port {
 	uint64_t time;                /* Current NIC TX time measured in bytes */
 	struct rte_reciprocal inv_cycles_per_byte; /* CPU cycles per byte */
+	uint64_t cycles_per_byte;
 
 	/* Scheduling loop detection */
@@ -683,4 +684,5 @@ rte_sched_port_config(struct rte_sched_port_params *params)
 		/ params->rate;
 	port->inv_cycles_per_byte = rte_reciprocal_value(cycles_per_byte);
+	port->cycles_per_byte = cycles_per_byte;
 
 	/* Scheduling loop detection */
@@ -2191,7 +2193,11 @@ rte_sched_port_time_resync(struct rte_sched_port *port)
 {
 	uint64_t cycles = rte_get_tsc_cycles();
-	uint64_t cycles_diff = cycles - port->time_cpu_cycles;
+	uint64_t cycles_diff;
 	uint64_t bytes_diff;
 
+	if (cycles < port->time_cpu_cycles)
+		port->time_cpu_cycles = 0;
+
+	cycles_diff = cycles - port->time_cpu_cycles;
 	/* Compute elapsed time in bytes */
 	bytes_diff = rte_reciprocal_divide(cycles_diff << RTE_SCHED_TIME_SHIFT,
@@ -2199,5 +2205,6 @@ rte_sched_port_time_resync(struct rte_sched_port *port)
 
 	/* Advance port time */
-	port->time_cpu_cycles = cycles;
+	port->time_cpu_cycles +=
+		(bytes_diff * port->cycles_per_byte) >> RTE_SCHED_TIME_SHIFT;
 	port->time_cpu_bytes += bytes_diff;
 	if (port->time < port->time_cpu_bytes)
-- 
2.21.3

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2020-07-17 17:17:01.165113282 +0100
+++ 0021-sched-fix-port-time-rounding.patch	2020-07-17 17:16:59.997771060 +0100
@@ -1 +1 @@
-From 83415d4fd88c925002655aa755601998a3cdef2c Mon Sep 17 00:00:00 2001
+From 38f30a1f450b56666f5339ee4e68f795cdf51b06 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 83415d4fd88c925002655aa755601998a3cdef2c ]
+
@@ -24 +25,0 @@
-Cc: stable@dpdk.org
@@ -33 +34 @@
-index 68a171b508..0fa0741664 100644
+index 89c3d1e7f7..d8ace20fe0 100644
@@ -36 +37 @@
-@@ -223,4 +223,5 @@ struct rte_sched_port {
+@@ -201,4 +201,5 @@ struct rte_sched_port {
@@ -41,2 +42,2 @@
- 	/* Grinders */
-@@ -853,4 +854,5 @@ rte_sched_port_config(struct rte_sched_port_params *params)
+ 	/* Scheduling loop detection */
+@@ -683,4 +684,5 @@ rte_sched_port_config(struct rte_sched_port_params *params)
@@ -47,2 +48,2 @@
- 	/* Grinders */
-@@ -2674,8 +2676,12 @@ rte_sched_port_time_resync(struct rte_sched_port *port)
+ 	/* Scheduling loop detection */
+@@ -2191,7 +2193,11 @@ rte_sched_port_time_resync(struct rte_sched_port *port)
@@ -54 +54,0 @@
- 	uint32_t i;
@@ -62 +62 @@
-@@ -2683,5 +2689,6 @@ rte_sched_port_time_resync(struct rte_sched_port *port)
+@@ -2199,5 +2205,6 @@ rte_sched_port_time_resync(struct rte_sched_port *port)


  parent reply	other threads:[~2020-07-17 16:33 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-17 16:31 [dpdk-stable] patch 'net/netvsc: do not spin forever waiting for reply' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'app/testpmd: fix memory leak on error path' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'net/mlx5: fix unreachable MPLS " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'net/failsafe: fix RSS RETA size info' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'net/i40e: enable NEON Rx/Tx in meson' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'net/cxgbe: fix CLIP leak in filter error path' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'bpf: fix add/sub min/max estimations' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'net: fix IPv4 checksum' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'examples: add flush after stats printing' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'bus/vmbus: fix ring buffer mapping' " Kevin Traynor
2020-07-17 16:31 ` [dpdk-stable] patch 'pci: fix address domain format size' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'net/qede: fix multicast drop in promiscuous mode' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'net/mvpp2: fix non-EAL thread support' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'eal/arm: add vcopyq intrinsic for aarch32' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'net/ixgbe: fix include of vector header file' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'net/mlx5: fix iterator type in Rx queue management' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'vhost: fix features definition location' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'mem: fix 32-bit init config with meson' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'examples/eventdev: fix 32-bit coremask' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'devtools: fix path in forbidden token check' " Kevin Traynor
2020-07-17 16:32 ` Kevin Traynor [this message]
2020-07-17 16:32 ` [dpdk-stable] patch 'lib: remind experimental status in headers' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'rawdev: remove remaining experimental tags' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'eal/armv8: fix timer frequency calibration with PMU' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'vfio: remove unused variable' " Kevin Traynor
2020-07-17 16:32 ` [dpdk-stable] patch 'eal: fix uuid header dependencies' " Kevin Traynor

Reply instructions:

You may reply publicly 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=20200717163214.4839-21-ktraynor@redhat.com \
    --to=ktraynor@redhat.com \
    --cc=alan.dewar@att.com \
    --cc=jasvinder.singh@intel.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

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://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/ https://inbox.dpdk.org/stable \
		stable@dpdk.org
	public-inbox-index stable

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.stable


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