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hyperv/hn: Reduce TCP segment aggregation limit for multiple RX rings

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This mainly used to improve ACK timeliness when multiple RX rings
are enabled.

This value gives the best performance in both Azure and Hyper-V
environment, w/ both 10Ge and 40Ge using non-{INVARIANTS,WITNESS}
kernel.

MFC after:	1 week
Sponsored by:	Microsoft OSTC
Differential Revision:	https://reviews.freebsd.org/D5691
This commit is contained in:
sephe 2016-03-22 06:31:39 +00:00
parent 96842098f8
commit de7ddcd5bb
1 changed files with 16 additions and 0 deletions
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16
sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
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@ -181,6 +181,7 @@ struct hn_txdesc {
#define HN_CSUM_ASSIST_WIN8 (CSUM_IP | CSUM_TCP)
#define HN_CSUM_ASSIST (CSUM_IP | CSUM_UDP | CSUM_TCP)
#define HN_LRO_LENLIM_MULTIRX_DEF (12 * ETHERMTU)
#define HN_LRO_LENLIM_DEF (25 * ETHERMTU)
/* YYY 2*MTU is a bit rough, but should be good enough. */
#define HN_LRO_LENLIM_MIN(ifp) (2 * (ifp)->if_mtu)
@ -530,6 +531,21 @@ netvsc_attach(device_t dev)
device_printf(dev, "%d TX ring, %d RX ring\n",
sc->hn_tx_ring_inuse, sc->hn_rx_ring_inuse);
#if __FreeBSD_version >= 1100099
if (sc->hn_rx_ring_inuse > 1) {
int i;
/*
* Reduce TCP segment aggregation limit for multiple
* RX rings to increase ACK timeliness.
*/
for (i = 0; i < sc->hn_rx_ring_inuse; ++i) {
sc->hn_rx_ring[i].hn_lro.lro_length_lim =
HN_LRO_LENLIM_MULTIRX_DEF;
}
}
#endif
if (device_info.link_state == 0) {
sc->hn_carrier = 1;
}