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authorBjørn Mork <bjorn@mork.no>2014-05-16 21:48:22 +0200
committerDavid S. Miller <davem@davemloft.net>2014-05-16 22:39:01 -0400
commit6c4e548ff36672eeb78f8288a2920d66fa4a6a66 (patch)
treefe2e6d17ffd63d02ee28d3a51e8a0b166ba1d311 /drivers/net/usb
parent68864abf08f06d7cbbabd03740beb383ccf5e5d5 (diff)
net: cdc_ncm: use ethtool to tune coalescing settings
Datagram coalescing is an integral part of the NCM and MBIM protocols, intended to reduce the interrupt load primarily on the device end of the USB link. As with all coalescing solutions, there is a trade-off between buffering and interrupts. The current defaults are based on the assumption that device side buffers should be the limiting factor. However, many modern high speed LTE modems suffers from buffer-bloat, making this assumption fail. This results in sub-optimal performance due to excessive coalescing. And in cases where such modems are connected to cheap embedded hosts there is often severe buffer allocation issues, giving very noticeable performance degradation . A start on improving this is going from build time hard coded limits to per device user configurable limits. The ethtool coalescing API was selected as user interface because, although the tuned values are buffer sizes, these settings directly control datagram coalescing. Signed-off-by: Bjørn Mork <bjorn@mork.no> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/usb')
-rw-r--r--drivers/net/usb/cdc_ncm.c71
1 files changed, 69 insertions, 2 deletions
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 2ec3790a4db8..141dbec912be 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -65,6 +65,67 @@ static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx);
static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *hr_timer);
static struct usb_driver cdc_ncm_driver;
+static int cdc_ncm_get_coalesce(struct net_device *netdev,
+ struct ethtool_coalesce *ec)
+{
+ struct usbnet *dev = netdev_priv(netdev);
+ struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
+
+ /* assuming maximum sized dgrams and ignoring NDPs */
+ ec->rx_max_coalesced_frames = ctx->rx_max / ctx->max_datagram_size;
+ ec->tx_max_coalesced_frames = ctx->tx_max / ctx->max_datagram_size;
+
+ /* the timer will fire CDC_NCM_TIMER_PENDING_CNT times in a row */
+ ec->tx_coalesce_usecs = (ctx->timer_interval * CDC_NCM_TIMER_PENDING_CNT) / NSEC_PER_USEC;
+ return 0;
+}
+
+static void cdc_ncm_update_rxtx_max(struct usbnet *dev, u32 new_rx, u32 new_tx);
+
+static int cdc_ncm_set_coalesce(struct net_device *netdev,
+ struct ethtool_coalesce *ec)
+{
+ struct usbnet *dev = netdev_priv(netdev);
+ struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
+ u32 new_rx_max = ctx->rx_max;
+ u32 new_tx_max = ctx->tx_max;
+
+ /* assuming maximum sized dgrams and a single NDP */
+ if (ec->rx_max_coalesced_frames)
+ new_rx_max = ec->rx_max_coalesced_frames * ctx->max_datagram_size;
+ if (ec->tx_max_coalesced_frames)
+ new_tx_max = ec->tx_max_coalesced_frames * ctx->max_datagram_size;
+
+ if (ec->tx_coalesce_usecs &&
+ (ec->tx_coalesce_usecs < CDC_NCM_TIMER_INTERVAL_MIN * CDC_NCM_TIMER_PENDING_CNT ||
+ ec->tx_coalesce_usecs > CDC_NCM_TIMER_INTERVAL_MAX * CDC_NCM_TIMER_PENDING_CNT))
+ return -EINVAL;
+
+ spin_lock_bh(&ctx->mtx);
+ ctx->timer_interval = ec->tx_coalesce_usecs * NSEC_PER_USEC / CDC_NCM_TIMER_PENDING_CNT;
+ if (!ctx->timer_interval)
+ ctx->tx_timer_pending = 0;
+ spin_unlock_bh(&ctx->mtx);
+
+ /* inform device of new values */
+ if (new_rx_max != ctx->rx_max || new_tx_max != ctx->tx_max)
+ cdc_ncm_update_rxtx_max(dev, new_rx_max, new_tx_max);
+ return 0;
+}
+
+static const struct ethtool_ops cdc_ncm_ethtool_ops = {
+ .get_settings = usbnet_get_settings,
+ .set_settings = usbnet_set_settings,
+ .get_link = usbnet_get_link,
+ .nway_reset = usbnet_nway_reset,
+ .get_drvinfo = usbnet_get_drvinfo,
+ .get_msglevel = usbnet_get_msglevel,
+ .set_msglevel = usbnet_set_msglevel,
+ .get_ts_info = ethtool_op_get_ts_info,
+ .get_coalesce = cdc_ncm_get_coalesce,
+ .set_coalesce = cdc_ncm_set_coalesce,
+};
+
/* handle rx_max and tx_max changes */
static void cdc_ncm_update_rxtx_max(struct usbnet *dev, u32 new_rx, u32 new_tx)
{
@@ -257,6 +318,9 @@ static int cdc_ncm_init(struct usbnet *dev)
(ctx->tx_max_datagrams > CDC_NCM_DPT_DATAGRAMS_MAX))
ctx->tx_max_datagrams = CDC_NCM_DPT_DATAGRAMS_MAX;
+ /* initial coalescing timer interval */
+ ctx->timer_interval = CDC_NCM_TIMER_INTERVAL_USEC * NSEC_PER_USEC;
+
return 0;
}
@@ -596,6 +660,9 @@ advance:
/* finish setting up the device specific data */
cdc_ncm_setup(dev);
+ /* override ethtool_ops */
+ dev->net->ethtool_ops = &cdc_ncm_ethtool_ops;
+
return 0;
error2:
@@ -863,7 +930,7 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
ctx->tx_curr_skb = skb_out;
goto exit_no_skb;
- } else if ((n < ctx->tx_max_datagrams) && (ready2send == 0)) {
+ } else if ((n < ctx->tx_max_datagrams) && (ready2send == 0) && (ctx->timer_interval > 0)) {
/* wait for more frames */
/* push variables */
ctx->tx_curr_skb = skb_out;
@@ -915,7 +982,7 @@ static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx)
/* start timer, if not already started */
if (!(hrtimer_active(&ctx->tx_timer) || atomic_read(&ctx->stop)))
hrtimer_start(&ctx->tx_timer,
- ktime_set(0, CDC_NCM_TIMER_INTERVAL),
+ ktime_set(0, ctx->timer_interval),
HRTIMER_MODE_REL);
}