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hyperv/hn: Avoid mbuf cluster allocation, if the packet is small.

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This one mainly avoids mbuf cluster allocation for TCP ACKs during
TCP sending tests.  And it gives me ~200Mbps improvement (4.7Gbps
-> 4.9Gbps), when running iperf3 TCP sending test w/ 16 connections.

While I'm here, nuke the unnecessary zeroing out pkthdr.csum_flags.

Reviewed by:		adrain
Approved by:		adrian (mentor)
Sponsored by:		Microsoft OSTC
Differential Revision:	https://reviews.freebsd.org/D4853
This commit is contained in:
Sepherosa Ziehau 2016-01-12 01:50:56 +00:00
parent da949700f2
commit c48d20d7c7
2 changed files with 31 additions and 25 deletions
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1
sys/dev/hyperv/netvsc/hv_net_vsc.h
View File

@ -1011,6 +1011,7 @@ typedef struct hn_softc {
u_long hn_csum_tcp;
u_long hn_csum_trusted;
u_long hn_lro_tried;
u_long hn_small_pkts;
} hn_softc_t;

55
sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
View File

@ -469,6 +469,8 @@ netvsc_attach(device_t dev)
SYSCTL_ADD_ULONG(ctx, child, OID_AUTO, "csum_trusted",
CTLFLAG_RW, &sc->hn_csum_trusted,
"# of TCP segements that we trust host's csum verification");
SYSCTL_ADD_ULONG(ctx, child, OID_AUTO, "small_pkts",
CTLFLAG_RW, &sc->hn_small_pkts, "# of small packets received");
if (unit == 0) {
struct sysctl_ctx_list *dc_ctx;
@ -1022,35 +1024,38 @@ netvsc_recv(struct hv_device *device_ctx, netvsc_packet *packet,
*/
if (packet->tot_data_buf_len > (ifp->if_mtu + ETHER_HDR_LEN)) {
return (0);
} else if (packet->tot_data_buf_len <= MHLEN) {
m_new = m_gethdr(M_NOWAIT, MT_DATA);
if (m_new == NULL)
return (0);
memcpy(mtod(m_new, void *), packet->data,
packet->tot_data_buf_len);
m_new->m_pkthdr.len = m_new->m_len = packet->tot_data_buf_len;
sc->hn_small_pkts++;
} else {
/*
* Get an mbuf with a cluster. For packets 2K or less,
* get a standard 2K cluster. For anything larger, get a
* 4K cluster. Any buffers larger than 4K can cause problems
* if looped around to the Hyper-V TX channel, so avoid them.
*/
size = MCLBYTES;
if (packet->tot_data_buf_len > MCLBYTES) {
/* 4096 */
size = MJUMPAGESIZE;
}
m_new = m_getjcl(M_NOWAIT, MT_DATA, M_PKTHDR, size);
if (m_new == NULL) {
device_printf(dev, "alloc mbuf failed.\n");
return (0);
}
hv_m_append(m_new, packet->tot_data_buf_len, packet->data);
}
/*
* Get an mbuf with a cluster. For packets 2K or less,
* get a standard 2K cluster. For anything larger, get a
* 4K cluster. Any buffers larger than 4K can cause problems
* if looped around to the Hyper-V TX channel, so avoid them.
*/
size = MCLBYTES;
if (packet->tot_data_buf_len > MCLBYTES) {
/* 4096 */
size = MJUMPAGESIZE;
}
m_new = m_getjcl(M_NOWAIT, MT_DATA, M_PKTHDR, size);
if (m_new == NULL) {
device_printf(dev, "alloc mbuf failed.\n");
return (0);
}
hv_m_append(m_new, packet->tot_data_buf_len,
packet->data);
m_new->m_pkthdr.rcvif = ifp;
/* receive side checksum offload */
m_new->m_pkthdr.csum_flags = 0;
if (NULL != csum_info) {
/* IP csum offload */
if (csum_info->receive.ip_csum_succeeded) {