| Message ID | 1490617879-14014-1-git-send-email-jonas.jensen@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
From: Jonas Jensen <jonas.jensen@gmail.com> Date: Mon, 27 Mar 2017 14:31:19 +0200 > @@ -25,6 +25,7 @@ > #include <linux/of_irq.h> > #include <linux/crc32.h> > #include <linux/crc32c.h> > +#include <linux/circ_buf.h> > > #include "moxart_ether.h" > > @@ -297,6 +298,7 @@ static void moxart_tx_finished(struct net_device *ndev) > tx_tail = TX_NEXT(tx_tail); > } > priv->tx_tail = tx_tail; > + netif_wake_queue(ndev); > } > > static irqreturn_t moxart_mac_interrupt(int irq, void *dev_id) Doing the wakeup unconditionally is very wasteful, you just need to do it when enough space has been made available. Therefore the wakeup should be more like: if (netif_queue_stopped(ndev) && moxart_tx_queue_space(ndev) >= MOXART_TX_WAKEUP_THRESHOLD) netif_wake_queue(); Otherwise you're just going to flap back and forth under high load and get almost not packet batching at all, hurting performance.
On 28 March 2017 at 05:50, David Miller <davem@davemloft.net> wrote: > Doing the wakeup unconditionally is very wasteful, you just need to do it > when enough space has been made available. Thanks, please see v3. Jonas
diff --git a/drivers/net/ethernet/moxa/moxart_ether.c b/drivers/net/ethernet/moxa/moxart_ether.c index 06c9f41..fa571d5 100644 --- a/drivers/net/ethernet/moxa/moxart_ether.c +++ b/drivers/net/ethernet/moxa/moxart_ether.c @@ -25,6 +25,7 @@ #include <linux/of_irq.h> #include <linux/crc32.h> #include <linux/crc32c.h> +#include <linux/circ_buf.h> #include "moxart_ether.h" @@ -297,6 +298,7 @@ static void moxart_tx_finished(struct net_device *ndev) tx_tail = TX_NEXT(tx_tail); } priv->tx_tail = tx_tail; + netif_wake_queue(ndev); } static irqreturn_t moxart_mac_interrupt(int irq, void *dev_id) @@ -324,13 +326,19 @@ static int moxart_mac_start_xmit(struct sk_buff *skb, struct net_device *ndev) struct moxart_mac_priv_t *priv = netdev_priv(ndev); void *desc; unsigned int len; - unsigned int tx_head = priv->tx_head; + unsigned int tx_head, tx_tail; u32 txdes1; int ret = NETDEV_TX_BUSY; + spin_lock_irq(&priv->txlock); + + tx_head = priv->tx_head; + tx_tail = priv->tx_tail; desc = priv->tx_desc_base + (TX_REG_DESC_SIZE * tx_head); - spin_lock_irq(&priv->txlock); + if (CIRC_SPACE(tx_head, tx_tail, TX_DESC_NUM) == 1) + netif_stop_queue(ndev); + if (moxart_desc_read(desc + TX_REG_OFFSET_DESC0) & TX_DESC0_DMA_OWN) { net_dbg_ratelimited("no TX space for packet\n"); priv->stats.tx_dropped++;
moxart_mac_start_xmit() doesn't care where tx_tail is, tx_head can catch and pass tx_tail, which is bad because moxart_tx_finished() isn't guaranteed to catch up on freeing resources from tx_tail. Add a check in moxart_mac_start_xmit() stopping the queue at the end of the circular buffer. Wake it on completion. Addresses https://bugzilla.kernel.org/show_bug.cgi?id=99451 Signed-off-by: Jonas Jensen <jonas.jensen@gmail.com> --- Notes: ChangeLog v1->v2: - stop queue instead of dropping frames The following trick was used to trigger the leak. On the host (where this driver runs): 1. iptables-restore /etc/iptables.conf && echo 1 > /proc/sys/net/ipv4/ip_forward && ifconfig eth0:0 192.168.5.1 2. cat /dev/zero | nc -l -p 3334 On a client configured with 192.168.5.1 as a gateway: 1. nc -v 192.168.5.1 3334 > /dev/null & repeat the following multiple times, interrup after a few seconds with CTRL+C: 2. wget http://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-8.7.1-amd64-netinst.iso Result (especially note columns <active_objs> and <num_objs> of kmalloc-192 and kmalloc-2048): date && ifconfig && echo 1 > /proc/sys/vm/drop_caches && cat /proc/slabinfo Fri Mar 24 16:22:54 CET 2017 .. RX bytes:57737 (56.3 KiB) TX bytes:6638 (6.4 KiB) .. # name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> : tunables <limit> .. .. kmalloc-8192 8 8 8192 4 8 : tunables 0 0 0 : slabdata 2 2 0 kmalloc-4096 13 16 4096 8 8 : tunables 0 0 0 : slabdata 2 2 0 kmalloc-2048 40 40 2048 8 4 : tunables 0 0 0 : slabdata 5 5 0 kmalloc-1024 94 96 1024 8 2 : tunables 0 0 0 : slabdata 12 12 0 kmalloc-512 179 184 512 8 1 : tunables 0 0 0 : slabdata 23 23 0 kmalloc-256 76 80 256 16 1 : tunables 0 0 0 : slabdata 5 5 0 kmalloc-192 126 126 192 21 1 : tunables 0 0 0 : slabdata 6 6 0 kmalloc-128 340 416 128 32 1 : tunables 0 0 0 : slabdata 13 13 0 kmalloc-96 8353 8358 96 42 1 : tunables 0 0 0 : slabdata 199 199 0 kmalloc-64 313 320 64 64 1 : tunables 0 0 0 : slabdata 5 5 0 kmalloc-32 1460 1536 32 128 1 : tunables 0 0 0 : slabdata 12 12 0 date && ifconfig && echo 1 > /proc/sys/vm/drop_caches && cat /proc/slabinfo Fri Mar 24 16:26:36 CET 2017 .. RX bytes:70381213 (67.1 MiB) TX bytes:86208719 (82.2 MiB) .. # name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> : tunables <limit> .. .. kmalloc-8192 8 8 8192 4 8 : tunables 0 0 0 : slabdata 2 2 0 kmalloc-4096 13 16 4096 8 8 : tunables 0 0 0 : slabdata 2 2 0 kmalloc-2048 2159 2194 2048 8 4 : tunables 0 0 0 : slabdata 275 275 0 kmalloc-1024 100 104 1024 8 2 : tunables 0 0 0 : slabdata 13 13 0 kmalloc-512 182 184 512 8 1 : tunables 0 0 0 : slabdata 23 23 0 kmalloc-256 76 80 256 16 1 : tunables 0 0 0 : slabdata 5 5 0 kmalloc-192 2638 2667 192 21 1 : tunables 0 0 0 : slabdata 127 127 0 kmalloc-128 344 416 128 32 1 : tunables 0 0 0 : slabdata 13 13 0 kmalloc-96 8353 8358 96 42 1 : tunables 0 0 0 : slabdata 199 199 0 kmalloc-64 313 320 64 64 1 : tunables 0 0 0 : slabdata 5 5 0 kmalloc-32 1625 1664 32 128 1 : tunables 0 0 0 : slabdata 13 13 0 Applies to next-20170310 drivers/net/ethernet/moxa/moxart_ether.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)