Commit d5a05e69 authored by Vincent Whitchurch's avatar Vincent Whitchurch Committed by Jakub Kicinski
Browse files

net: stmmac: Use hrtimer for TX coalescing 



This driver uses a normal timer for TX coalescing, which means that the
with the default tx-usecs of 1000 microseconds the cleanups actually
happen 10 ms or more later with HZ=100.  This leads to very low
througput with TCP when bridged to a slow link such as a 4G modem.  Fix
this by using an hrtimer instead.

On my ARM platform with HZ=100 and the default TX coalescing settings
(tx-frames 25 tx-usecs 1000), with "tc qdisc add dev eth0 root netem
delay 60ms 40ms rate 50Mbit" run on the server, netperf's TCP_STREAM
improves from ~5.5 Mbps to ~100 Mbps.

Signed-off-by: default avatarVincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20201120150208.6838-1-vincent.whitchurch@axis.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 5112cf59

drivers/net/ethernet/stmicro/stmmac/stmmac.h

+2 −1
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#define DRV_MODULE_VERSION	"Jan_2016"



#include <linux/clk.h>

#include <linux/hrtimer.h>

#include <linux/if_vlan.h>

#include <linux/stmmac.h>

#include <linux/phylink.h>
@@ -46,7 +47,7 @@ struct stmmac_tx_info { 
struct stmmac_tx_queue {

	u32 tx_count_frames;

	int tbs;

	struct timer_list txtimer;

	struct hrtimer txtimer;

	u32 queue_index;

	struct stmmac_priv *priv_data;

	struct dma_extended_desc *dma_etx ____cacheline_aligned_in_smp;

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

+14 −9
Original line number Diff line number Diff line
@@ -111,7 +111,7 @@ static void stmmac_init_fs(struct net_device *dev); 
static void stmmac_exit_fs(struct net_device *dev);

#endif



#define STMMAC_COAL_TIMER(x) (jiffies + usecs_to_jiffies(x))

#define STMMAC_COAL_TIMER(x) (ns_to_ktime((x) * NSEC_PER_USEC))



/**

 * stmmac_verify_args - verify the driver parameters.
@@ -2076,7 +2076,8 @@ static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue) 


	/* We still have pending packets, let's call for a new scheduling */

	if (tx_q->dirty_tx != tx_q->cur_tx)

		mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(priv->tx_coal_timer));

		hrtimer_start(&tx_q->txtimer, STMMAC_COAL_TIMER(priv->tx_coal_timer),

			      HRTIMER_MODE_REL);



	__netif_tx_unlock_bh(netdev_get_tx_queue(priv->dev, queue));
@@ -2360,7 +2361,8 @@ static void stmmac_tx_timer_arm(struct stmmac_priv *priv, u32 queue) 
{

	struct stmmac_tx_queue *tx_q = &priv->tx_queue[queue];



	mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(priv->tx_coal_timer));

	hrtimer_start(&tx_q->txtimer, STMMAC_COAL_TIMER(priv->tx_coal_timer),

		      HRTIMER_MODE_REL);

}



/**
@@ -2369,9 +2371,9 @@ static void stmmac_tx_timer_arm(struct stmmac_priv *priv, u32 queue) 
 * Description:

 * This is the timer handler to directly invoke the stmmac_tx_clean.

 */

static void stmmac_tx_timer(struct timer_list *t)

static enum hrtimer_restart stmmac_tx_timer(struct hrtimer *t)

{

	struct stmmac_tx_queue *tx_q = from_timer(tx_q, t, txtimer);

	struct stmmac_tx_queue *tx_q = container_of(t, struct stmmac_tx_queue, txtimer);

	struct stmmac_priv *priv = tx_q->priv_data;

	struct stmmac_channel *ch;
@@ -2385,6 +2387,8 @@ static void stmmac_tx_timer(struct timer_list *t) 
		spin_unlock_irqrestore(&ch->lock, flags);

		__napi_schedule(&ch->tx_napi);

	}



	return HRTIMER_NORESTART;

}



/**
@@ -2407,7 +2411,8 @@ static void stmmac_init_coalesce(struct stmmac_priv *priv) 
	for (chan = 0; chan < tx_channel_count; chan++) {

		struct stmmac_tx_queue *tx_q = &priv->tx_queue[chan];



		timer_setup(&tx_q->txtimer, stmmac_tx_timer, 0);

		hrtimer_init(&tx_q->txtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

		tx_q->txtimer.function = stmmac_tx_timer;

	}

}
@@ -2899,7 +2904,7 @@ static int stmmac_open(struct net_device *dev) 
	phylink_stop(priv->phylink);



	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)

		del_timer_sync(&priv->tx_queue[chan].txtimer);

		hrtimer_cancel(&priv->tx_queue[chan].txtimer);



	stmmac_hw_teardown(dev);

init_error:
@@ -2932,7 +2937,7 @@ static int stmmac_release(struct net_device *dev) 
	stmmac_disable_all_queues(priv);



	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)

		del_timer_sync(&priv->tx_queue[chan].txtimer);

		hrtimer_cancel(&priv->tx_queue[chan].txtimer);



	/* Free the IRQ lines */

	free_irq(dev->irq, dev);
@@ -5165,7 +5170,7 @@ int stmmac_suspend(struct device *dev) 
	stmmac_disable_all_queues(priv);



	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)

		del_timer_sync(&priv->tx_queue[chan].txtimer);

		hrtimer_cancel(&priv->tx_queue[chan].txtimer);



	/* Stop TX/RX DMA */

	stmmac_stop_all_dma(priv);