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authorBjørn Mork <bjorn@mork.no>2014-05-16 23:48:22 +0400
committerDavid S. Miller <davem@davemloft.net>2014-05-17 06:39:01 +0400
commit6c4e548ff36672eeb78f8288a2920d66fa4a6a66 (patch)
treefe2e6d17ffd63d02ee28d3a51e8a0b166ba1d311 /include/linux/usb
parent68864abf08f06d7cbbabd03740beb383ccf5e5d5 (diff)
downloadlinux-6c4e548ff36672eeb78f8288a2920d66fa4a6a66.tar.xz
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 'include/linux/usb')
-rw-r--r--include/linux/usb/cdc_ncm.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index 55b6feead93b..5c1066b4dc41 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -72,7 +72,9 @@
/* Restart the timer, if amount of datagrams is less than given value */
#define CDC_NCM_RESTART_TIMER_DATAGRAM_CNT 3
#define CDC_NCM_TIMER_PENDING_CNT 2
-#define CDC_NCM_TIMER_INTERVAL (400UL * NSEC_PER_USEC)
+#define CDC_NCM_TIMER_INTERVAL_USEC 400UL
+#define CDC_NCM_TIMER_INTERVAL_MIN 5UL
+#define CDC_NCM_TIMER_INTERVAL_MAX (15UL * USEC_PER_SEC)
/* The following macro defines the minimum header space */
#define CDC_NCM_MIN_HDR_SIZE \
@@ -107,6 +109,8 @@ struct cdc_ncm_ctx {
spinlock_t mtx;
atomic_t stop;
+ u64 timer_interval;
+
u32 tx_timer_pending;
u32 tx_curr_frame_num;
u32 rx_max;