999-01-net-introduce-napi_is_scheduled-helper.patch

From b5532bdc6d09e6e789417f0c7a0b665b57b0e7be Mon Sep 17 00:00:00 2001
From: Christian Marangi <ansuelsmth@gmail.com>
Date: Mon, 18 Sep 2023 14:21:56 +0200
Subject: [PATCH 1/3] net: introduce napi_is_scheduled helper

We currently have napi_if_scheduled_mark_missed that can be used to
check if napi is scheduled but that does more thing than simply checking
it and return a bool. Some driver already implement custom function to
check if napi is scheduled.

Drop these custom function and introduce napi_is_scheduled that simply
check if napi is scheduled atomically.

Update any driver and code that implement a similar check and instead
use this new helper.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/net/ethernet/chelsio/cxgb3/sge.c  | 8 --------
 drivers/net/wireless/realtek/rtw89/core.c | 2 +-
 include/linux/netdevice.h                 | 5 +++++
 net/core/dev.c                            | 2 +-
 4 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb3/sge.c b/drivers/net/ethernet/chelsio/cxgb3/sge.c
index 2e9a74fe0970..71fa2dc19034 100644
--- a/drivers/net/ethernet/chelsio/cxgb3/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb3/sge.c
@@ -2501,14 +2501,6 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
 	return work_done;
 }
 
-/*
- * Returns true if the device is already scheduled for polling.
- */
-static inline int napi_is_scheduled(struct napi_struct *napi)
-{
-	return test_bit(NAPI_STATE_SCHED, &napi->state);
-}
-
 /**
  *	process_pure_responses - process pure responses from a response queue
  *	@adap: the adapter
diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index 133bf289bacb..bbf4ea3639d4 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1744,7 +1744,7 @@ static void rtw89_core_rx_to_mac80211(struct rtw89_dev *rtwdev,
 	struct napi_struct *napi = &rtwdev->napi;
 
 	/* In low power mode, napi isn't scheduled. Receive it to netif. */
-	if (unlikely(!test_bit(NAPI_STATE_SCHED, &napi->state)))
+	if (unlikely(!napi_is_scheduled(napi)))
 		napi = NULL;
 
 	rtw89_core_hw_to_sband_rate(rx_status);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index db3d8429d50d..8eac00cd3b92 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -482,6 +482,11 @@ static inline bool napi_prefer_busy_poll(struct napi_struct *n)
 	return test_bit(NAPI_STATE_PREFER_BUSY_POLL, &n->state);
 }
 
+static inline bool napi_is_scheduled(struct napi_struct *n)
+{
+	return test_bit(NAPI_STATE_SCHED, &n->state);
+}
+
 bool napi_schedule_prep(struct napi_struct *n);
 
 /**
diff --git a/net/core/dev.c b/net/core/dev.c
index cc03a5758d2d..32ba8002f65a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6523,7 +6523,7 @@ static int __napi_poll(struct napi_struct *n, bool *repoll)
 	 * accidentally calling ->poll() when NAPI is not scheduled.
 	 */
 	work = 0;
-	if (test_bit(NAPI_STATE_SCHED, &n->state)) {
+	if (napi_is_scheduled(n)) {
 		work = n->poll(n, weight);
 		trace_napi_poll(n, work, weight);
 	}
-- 
2.40.1

999-02-net-stmmac-improve-TX-timer-arm-logic.patch

From 26e872db0f14c09ab57486b538ecc3a24c579df2 Mon Sep 17 00:00:00 2001
From: Christian Marangi <ansuelsmth@gmail.com>
Date: Mon, 18 Sep 2023 14:39:01 +0200
Subject: [PATCH 2/3] net: stmmac: improve TX timer arm logic

There is currently a problem with the TX timer getting armed multiple
unnecessary times causing big performance regression on some device that
suffer from heavy handling of hrtimer rearm.

The use of the TX timer is an old implementation that predates the napi
implementation and the interrupt enable/disable handling.

Due to stmmac being a very old code, the TX timer was never evaluated
again with this new implementation and was kept there causing
performance regression. The performance regression started to appear
with kernel version 4.19 with 8fce33317023 ("net: stmmac: Rework coalesce
timer and fix multi-queue races") where the timer was reduced to 1ms
causing it to be armed 40 times more than before.

Decreasing the timer made the problem more present and caused the
regression in the other of 600-700mbps on some device (regression where
this was notice is ipq806x).

The problem is in the fact that handling the hrtimer on some target is
expensive and recent kernel made the timer armed much more times.
A solution that was proposed was reverting the hrtimer change and use
mod_timer but such solution would still hide the real problem in the
current implementation.

To fix the regression, apply some additional logic and skip arming the
timer when not needed.

Arm the timer ONLY if a napi is not already scheduled. Running the timer
is redundant since the same function (stmmac_tx_clean) will run in the
napi TX poll. Also try to cancel any timer if a napi is scheduled to
prevent redundant run of TX call.

With the following new logic the original performance are restored while
keeping using the hrtimer.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c  | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 9201ed778ebc..14bf6fae6662 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2994,13 +2994,25 @@ static void stmmac_tx_timer_arm(struct stmmac_priv *priv, u32 queue)
 {
 	struct stmmac_tx_queue *tx_q = &priv->dma_conf.tx_queue[queue];
 	u32 tx_coal_timer = priv->tx_coal_timer[queue];
+	struct stmmac_channel *ch;
+	struct napi_struct *napi;
 
 	if (!tx_coal_timer)
 		return;
 
-	hrtimer_start(&tx_q->txtimer,
-		      STMMAC_COAL_TIMER(tx_coal_timer),
-		      HRTIMER_MODE_REL);
+	ch = &priv->channel[tx_q->queue_index];
+	napi = tx_q->xsk_pool ? &ch->rxtx_napi : &ch->tx_napi;
+
+	/* Arm timer only if napi is not already scheduled.
+	 * Try to cancel any timer if napi is scheduled, timer will be armed
+	 * again in the next scheduled napi.
+	 */
+	if (unlikely(!napi_is_scheduled(napi)))
+		hrtimer_start(&tx_q->txtimer,
+			      STMMAC_COAL_TIMER(tx_coal_timer),
+			      HRTIMER_MODE_REL);
+	else
+		hrtimer_try_to_cancel(&tx_q->txtimer);
 }
 
 /**
-- 
2.40.1

999-03-net-stmmac-increase-TX-coalesce-timer-to-5ms.patch

From 13e24b0c4318b8b4d0a0fde7e5e7ccb982821c63 Mon Sep 17 00:00:00 2001
From: Christian Marangi <ansuelsmth@gmail.com>
Date: Mon, 18 Sep 2023 15:11:13 +0200
Subject: [PATCH 3/3] net: stmmac: increase TX coalesce timer to 5ms

Commit 8fce33317023 ("net: stmmac: Rework coalesce timer and fix
multi-queue races") decreased the TX coalesce timer from 40ms to 1ms.

This caused some performance regression on some target (regression was
reported at least on ipq806x) in the order of 600mbps dropping from
gigabit handling to only 200mbps.

The problem was identified in the TX timer getting armed too much time.
While this was fixed and improved in another commit, performance can be
improved even further by increasing the timer delay a bit moving from
1ms to 5ms.

The value is a good balance between battery saving by prevending too
much interrupt to be generated and permitting good performance for
internet oriented devices.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/net/ethernet/stmicro/stmmac/common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
index 403cb397d4d3..2d9f895c2193 100644
--- a/drivers/net/ethernet/stmicro/stmmac/common.h
+++ b/drivers/net/ethernet/stmicro/stmmac/common.h
@@ -290,7 +290,7 @@ struct stmmac_safety_stats {
 #define MIN_DMA_RIWT		0x10
 #define DEF_DMA_RIWT		0xa0
 /* Tx coalesce parameters */
-#define STMMAC_COAL_TX_TIMER	1000
+#define STMMAC_COAL_TX_TIMER	5000
 #define STMMAC_MAX_COAL_TX_TICK	100000
 #define STMMAC_TX_MAX_FRAMES	256
 #define STMMAC_TX_FRAMES	25
-- 
2.40.1