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Date: Mon, 21 Oct 2013 15:52:12 +0200
From: Giuseppe CAVALLARO <peppe.cavallaro@...com>
To: Jimmy Perchet <jimmy.perchet@...rot.com>
Cc: <netdev@...r.kernel.org>
Subject: Re: [PATCH RFC 5/5] net:stmmac: asynchronous tx_clean
Hello Jimmy
On 10/16/2013 5:24 PM, Jimmy Perchet wrote:
> Tx descriptor's cleanup and preparation are serialized, which is not necessary
> and decrease performance.
> In addition TX descriptor's cleanup is performed on NET_RX softirq, this is
> confusing.
hmm, here you are changing the logic behind the tx/rx processes.
As done in many drivers, the stmmac cleans the tx resources in
NAPI context and this is not a confuse approach ;-).
It gave me some performance improvements especially on TCP benchmarks.
> This patch unserialize tx descriptor's cleanup and preparation
> and defer cleanup in workqueue.
So you decide to use workqueue and I kindly ask you to give me more
details about the performance improvements (UDP/TCP) and cpu usage.
I can try to do some tests on my side too. This could take a while
unfortunately.
peppe
>
> Signed-off-by: Jimmy Perchet <jimmy.perchet@...rot.com>
> ---
> drivers/net/ethernet/stmicro/stmmac/chain_mode.c | 6 +--
> drivers/net/ethernet/stmicro/stmmac/stmmac.h | 6 ++-
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 52 +++++++++++++----------
> 3 files changed, 37 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
> index d6ed0ce..8ab83cb 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
> @@ -120,7 +120,7 @@ static void stmmac_refill_desc3(void *priv_ptr, struct dma_desc *p)
> * to keep explicit chaining in the descriptor.
> */
> p->des3 = (unsigned int)(priv->dma_rx_phy +
> - (((priv->dirty_rx) + 1) %
> + ((priv->dirty_rx + 1) %
> priv->dma_rx_size) *
> sizeof(struct dma_desc));
> }
> @@ -135,9 +135,9 @@ static void stmmac_clean_desc3(void *priv_ptr, struct dma_desc *p)
> * to keep explicit chaining in the descriptor.
> */
> p->des3 = (unsigned int)(priv->dma_tx_phy +
> - (((priv->dirty_tx + 1) %
> + ((atomic_read(&priv->dirty_tx) + 1) %
> priv->dma_tx_size) *
> - sizeof(struct dma_desc)));
> + sizeof(struct dma_desc));
> }
>
> const struct stmmac_chain_mode_ops chain_mode_ops = {
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> index f16a9bd..d5b8906 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> @@ -38,8 +38,8 @@ struct stmmac_priv {
> struct dma_extended_desc *dma_etx ____cacheline_aligned_in_smp;
> struct dma_desc *dma_tx;
> struct sk_buff **tx_skbuff;
> - unsigned int cur_tx;
> - unsigned int dirty_tx;
> + atomic_t cur_tx;
> + atomic_t dirty_tx;
> unsigned int dma_tx_size;
> u32 tx_count_frames;
> u32 tx_coal_frames;
> @@ -106,6 +106,8 @@ struct stmmac_priv {
> u32 adv_ts;
> int use_riwt;
> spinlock_t ptp_lock;
> + struct work_struct txclean_work;
> + struct workqueue_struct *wq;
> };
>
> extern int phyaddr;
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 5873246..de614ad 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -48,6 +48,7 @@
> #include <linux/seq_file.h>
> #endif /* CONFIG_STMMAC_DEBUG_FS */
> #include <linux/net_tstamp.h>
> +#include <linux/workqueue.h>
> #include "stmmac_ptp.h"
> #include "stmmac.h"
>
> @@ -205,7 +206,8 @@ static void print_pkt(unsigned char *buf, int len)
>
> static inline u32 stmmac_tx_avail(struct stmmac_priv *priv)
> {
> - return priv->dirty_tx + priv->dma_tx_size - priv->cur_tx - 1;
> + return atomic_read(&priv->dirty_tx) + priv->dma_tx_size
> + - atomic_read(&priv->cur_tx) - 1;
> }
>
> /**
> @@ -230,7 +232,7 @@ static inline void stmmac_hw_fix_mac_speed(struct stmmac_priv *priv)
> static void stmmac_enable_eee_mode(struct stmmac_priv *priv)
> {
> /* Check and enter in LPI mode */
> - if ((priv->dirty_tx == priv->cur_tx) &&
> + if ((atomic_read(&priv->dirty_tx) == atomic_read(&priv->cur_tx)) &&
> (priv->tx_path_in_lpi_mode == false))
> priv->hw->mac->set_eee_mode(priv->ioaddr);
> }
> @@ -1118,8 +1120,8 @@ static int init_dma_desc_rings(struct net_device *dev)
> priv->tx_skbuff[i] = NULL;
> }
>
> - priv->dirty_tx = 0;
> - priv->cur_tx = 0;
> + atomic_set(&priv->dirty_tx, 0);
> + atomic_set(&priv->cur_tx, 0);
>
> stmmac_clear_descriptors(priv);
>
> @@ -1264,17 +1266,17 @@ static void stmmac_dma_operation_mode(int mtu, struct stmmac_priv *priv)
> * @priv: driver private structure
> * Description: it reclaims resources after transmission completes.
> */
> -static void stmmac_tx_clean(struct stmmac_priv *priv)
> +static void stmmac_tx_clean(struct work_struct *work)
> {
> + struct stmmac_priv *priv =
> + container_of(work, struct stmmac_priv, txclean_work);
> unsigned int txsize = priv->dma_tx_size;
>
> - spin_lock(&priv->tx_lock);
> -
> priv->xstats.tx_clean++;
>
> - while (priv->dirty_tx != priv->cur_tx) {
> + while (atomic_read(&priv->dirty_tx) != atomic_read(&priv->cur_tx)) {
> int last;
> - unsigned int entry = priv->dirty_tx % txsize;
> + unsigned int entry = atomic_read(&priv->dirty_tx) % txsize;
> struct sk_buff *skb = priv->tx_skbuff[entry];
> struct dma_desc *p;
>
> @@ -1308,7 +1310,8 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
> }
> if (netif_msg_tx_done(priv))
> pr_debug("%s: curr %d, dirty %d\n", __func__,
> - priv->cur_tx, priv->dirty_tx);
> + atomic_read(&priv->cur_tx),
> + atomic_read(&priv->dirty_tx));
>
> if (likely(priv->tx_skbuff_dma[entry])) {
> dma_unmap_single(priv->device,
> @@ -1326,7 +1329,8 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
>
> priv->hw->desc->release_tx_desc(p, priv->mode);
>
> - priv->dirty_tx++;
> + wmb();
> + atomic_inc(&priv->dirty_tx);
> }
> if (unlikely(netif_queue_stopped(priv->dev) &&
> stmmac_tx_avail(priv) > STMMAC_TX_THRESH(priv))) {
> @@ -1344,7 +1348,6 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
> stmmac_enable_eee_mode(priv);
> mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(eee_timer));
> }
> - spin_unlock(&priv->tx_lock);
> }
>
> static inline void stmmac_enable_dma_irq(struct stmmac_priv *priv)
> @@ -1380,8 +1383,8 @@ static void stmmac_tx_err(struct stmmac_priv *priv)
> priv->hw->desc->init_tx_desc(&priv->dma_tx[i],
> priv->mode,
> (i == txsize - 1));
> - priv->dirty_tx = 0;
> - priv->cur_tx = 0;
> + atomic_set(&priv->dirty_tx, 0);
> + atomic_set(&priv->cur_tx, 0);
> priv->hw->dma->start_tx(priv->ioaddr);
>
> priv->dev->stats.tx_errors++;
> @@ -1401,12 +1404,16 @@ static void stmmac_dma_interrupt(struct stmmac_priv *priv)
> int status;
>
> status = priv->hw->dma->dma_interrupt(priv->ioaddr, &priv->xstats);
> - if (likely((status & handle_rx)) || (status & handle_tx)) {
> + if (likely(status & handle_rx)) {
> if (likely(napi_schedule_prep(&priv->napi))) {
> stmmac_disable_dma_irq(priv);
> __napi_schedule(&priv->napi);
> }
> }
> + if (likely(status & handle_tx))
> + queue_work(priv->wq, &priv->txclean_work);
> +
> +
> if (unlikely(status & tx_hard_error_bump_tc)) {
> /* Try to bump up the dma threshold on this failure */
> if (unlikely(tc != SF_DMA_MODE) && (tc <= 256)) {
> @@ -1596,8 +1603,7 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
> static void stmmac_tx_timer(unsigned long data)
> {
> struct stmmac_priv *priv = (struct stmmac_priv *)data;
> -
> - stmmac_tx_clean(priv);
> + queue_work(priv->wq, &priv->txclean_work);
> }
>
> /**
> @@ -1876,7 +1882,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
> if (priv->tx_path_in_lpi_mode)
> stmmac_disable_eee_mode(priv);
>
> - first_entry = entry = priv->cur_tx % txsize;
> + first_entry = entry = atomic_read(&priv->cur_tx) % txsize;
>
> csum_insertion = (skb->ip_summed == CHECKSUM_PARTIAL);
> /* To program the descriptors according to the size of the frame */
> @@ -1944,12 +1950,13 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
> priv->hw->desc->set_tx_owner(first);
> wmb();
>
> - priv->cur_tx += nb_desc;
> + atomic_add(nb_desc, &priv->cur_tx);
>
> if (netif_msg_pktdata(priv)) {
> pr_debug("%s: curr %d dirty=%d entry=%d, first=%p, nfrags=%d",
> - __func__, (priv->cur_tx % txsize),
> - (priv->dirty_tx % txsize), entry, first, nfrags);
> + __func__, (atomic_read(&priv->cur_tx) % txsize),
> + (atomic_read(&priv->dirty_tx) % txsize), entry,
> + first, nfrags);
>
> if (priv->extend_desc)
> stmmac_display_ring((void *)priv->dma_etx, txsize, 1);
> @@ -2171,7 +2178,6 @@ static int stmmac_poll(struct napi_struct *napi, int budget)
> int work_done = 0;
>
> priv->xstats.napi_poll++;
> - stmmac_tx_clean(priv);
>
> work_done = stmmac_rx(priv, budget);
> if (work_done < budget) {
> @@ -2747,6 +2753,8 @@ struct stmmac_priv *stmmac_dvr_probe(struct device *device,
>
> spin_lock_init(&priv->lock);
> spin_lock_init(&priv->tx_lock);
> + priv->wq = create_singlethread_workqueue("stmmac_wq");
> + INIT_WORK(&priv->txclean_work, stmmac_tx_clean);
>
> ret = register_netdev(ndev);
> if (ret) {
>
--
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