On 2014/12/16 16:54, Arnd Bergmann wrote: > On Tuesday 16 December 2014 15:57:21 Ding Tianhong wrote: >> On 2014/12/15 21:29, Arnd Bergmann wrote: >>> On Thursday 11 December 2014 19:42:27 Ding Tianhong wrote: >>> @@ -381,57 +392,37 @@ static void hip04_tx_reclaim(struct net_device *ndev, >>> bool force) >>> dev_kfree_skb(priv->tx_skb[tx_tail]); >>> priv->tx_skb[tx_tail] = NULL; >>> tx_tail = TX_NEXT(tx_tail); >>> - priv->tx_count--; >>> - >>> - if (priv->tx_count <= 0) >>> - break; >>> + count--; >>> } >>> > ... >>> - queue_delayed_work(priv->wq, &priv->tx_clean_task, delta_in_ticks); >>> + return count; >> >> I think should return pkts_compl, because may break from the loop, the >> pkts_compl may smaller than count. > > The calling convention I used is to return the packets that are remaining > on the queue. Only if that is nonzero we need to reschedule the timer. >
OK, agree. >> and we need to add netif_tx_lock() to protect this function to avoid >> concurrency conflict. > > Oh, did I miss something? The idea was that the start_xmit function only > updates > the tx_head pointer and reads the tx_tail, while the tx_reclaim function does > the reverse, and writes to a different cache line, in order to allow a > lockless > queue traversal. > > Can you point to a specific struct member that still need to be protected by > the lock? Did I miss a race that would allow both functions to exit with > the timer disabled and entries left on the queue? > OK, got it, no problem. >>> @@ -623,8 +648,6 @@ static int hip04_mac_stop(struct net_device *ndev) >>> struct hip04_priv *priv = netdev_priv(ndev); >>> int i; >>> >>> - cancel_delayed_work_sync(&priv->tx_clean_task); >>> - >> I think we should cancle the hrtimer when closed and queue the timer when >> open. > > I was expecting that force-cleaning up the tx queue would be enough for that. > It it not? > > I suppose it can't hurt to cancel the timer here anyway, and maybe use > WARN_ON() if it's still active. > Ok, I found no need to worry about this, when the dev is closed, the napi will disable and will not enter timer again. > Starting the timer after opening seems wrong though: at that point there are > no packets on the queue yet. The timer should always start ticking at the > exact point when the first packet is put on the queue while the timer is > not already pending. > Ok. >>> napi_disable(&priv->napi); >>> netif_stop_queue(ndev); >>> hip04_mac_disable(ndev); >>> @@ -725,6 +748,7 @@ static int hip04_mac_probe(struct platform_device *pdev) >>> struct hip04_priv *priv; >>> struct resource *res; >>> unsigned int irq; >>> + ktime_t txtime; >>> int ret; >>> >>> ndev = alloc_etherdev(sizeof(struct hip04_priv)); >>> @@ -751,6 +775,21 @@ static int hip04_mac_probe(struct platform_device >>> *pdev) >>> priv->port = arg.args[0]; >>> priv->chan = arg.args[1] * RX_DESC_NUM; >>> >>> + hrtimer_init(&priv->tx_coalesce_timer, CLOCK_MONOTONIC, >>> HRTIMER_MODE_REL); >>> + >>> + /* >>> + * BQL will try to keep the TX queue as short as possible, but it can't >>> + * be faster than tx_coalesce_usecs, so we need a fast timeout here, >>> + * but also long enough to gather up enough frames to ensure we don't >>> + * get more interrupts than necessary. >>> + * 200us is enough for 16 frames of 1500 bytes at gigabit ethernet rate >>> + */ >>> + priv->tx_coalesce_frames = TX_DESC_NUM * 3 / 4; >>> + priv->tx_coalesce_usecs = 200; >>> + /* allow timer to fire after half the time at the earliest */ >>> + txtime = ktime_set(0, priv->tx_coalesce_usecs * NSEC_PER_USEC / 2); >>> + hrtimer_set_expires_range(&priv->tx_coalesce_timer, txtime, txtime); >>> + >> >> I think miss the line: >> priv->tx_coalesce_timer.function = tx_done; > > Yes, good point. > I will send v10 when the net-next open again, and these days will test this driver, thanks a lot. Ding > Arnd > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > > . > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
