sepherosa_gmail.com created this revision.
sepherosa_gmail.com added reviewers: network, adrian, delphij, royger,
decui_microsoft.com, honzhan_microsoft.com, howard0su_gmail.com.
sepherosa_gmail.com added subscribers: freebsd-net-list,
freebsd-virtualization-list.
REVISION SUMMARY
So one spinlock is avoided, which would be potentially dangerous for virtual
machine, if the spinlock holder was scheduled out by the host as noted by
royger.
Old spinlock based txdesc list is still kept around, so we could have a safe
fallback.
No performance regression or improvement is observed.
REVISION DETAIL
https://reviews.freebsd.org/D5290
AFFECTED FILES
sys/dev/hyperv/netvsc/hv_net_vsc.h
sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
EMAIL PREFERENCES
https://reviews.freebsd.org/settings/panel/emailpreferences/
To: sepherosa_gmail.com, network, adrian, delphij, royger, decui_microsoft.com,
honzhan_microsoft.com, howard0su_gmail.com
Cc: freebsd-virtualization-list, freebsd-net-list
diff --git a/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c b/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
--- a/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
+++ b/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
@@ -70,6 +70,7 @@
#include <sys/lock.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
+#include <sys/buf_ring.h>
#include <net/if.h>
#include <net/if_arp.h>
@@ -151,7 +152,9 @@
#define HN_DIRECT_TX_SIZE_DEF 128
struct hn_txdesc {
+#ifndef HN_USE_TXDESC_BUFRING
SLIST_ENTRY(hn_txdesc) link;
+#endif
struct mbuf *m;
struct hn_tx_ring *txr;
int refs;
@@ -258,6 +261,14 @@
static struct taskqueue *hn_tx_taskq;
+#ifndef HN_USE_TXDESC_BUFRING
+static int hn_use_txdesc_bufring = 0;
+#else
+static int hn_use_txdesc_bufring = 1;
+#endif
+SYSCTL_INT(_hw_hn, OID_AUTO, use_txdesc_bufring, CTLFLAG_RD,
+ &hn_use_txdesc_bufring, 0, "Use buf_ring for TX descriptors");
+
/*
* Forward declarations
*/
@@ -570,13 +581,18 @@
txd->flags |= HN_TXD_FLAG_ONLIST;
+#ifndef HN_USE_TXDESC_BUFRING
mtx_lock_spin(&txr->hn_txlist_spin);
KASSERT(txr->hn_txdesc_avail >= 0 &&
txr->hn_txdesc_avail < txr->hn_txdesc_cnt,
("txdesc_put: invalid txd avail %d", txr->hn_txdesc_avail));
txr->hn_txdesc_avail++;
SLIST_INSERT_HEAD(&txr->hn_txlist, txd, link);
mtx_unlock_spin(&txr->hn_txlist_spin);
+#else
+ atomic_add_int(&txr->hn_txdesc_avail, 1);
+ buf_ring_enqueue(txr->hn_txdesc_br, txd);
+#endif
return 1;
}
@@ -586,6 +602,7 @@
{
struct hn_txdesc *txd;
+#ifndef HN_USE_TXDESC_BUFRING
mtx_lock_spin(&txr->hn_txlist_spin);
txd = SLIST_FIRST(&txr->hn_txlist);
if (txd != NULL) {
@@ -595,8 +612,14 @@
SLIST_REMOVE_HEAD(&txr->hn_txlist, link);
}
mtx_unlock_spin(&txr->hn_txlist_spin);
+#else
+ txd = buf_ring_dequeue_sc(txr->hn_txdesc_br);
+#endif
if (txd != NULL) {
+#ifdef HN_USE_TXDESC_BUFRING
+ atomic_subtract_int(&txr->hn_txdesc_avail, 1);
+#endif
KASSERT(txd->m == NULL && txd->refs == 0 &&
(txd->flags & HN_TXD_FLAG_ONLIST), ("invalid txd"));
txd->flags &= ~HN_TXD_FLAG_ONLIST;
@@ -2048,13 +2071,20 @@
txr->hn_sc = sc;
+#ifndef HN_USE_TXDESC_BUFRING
mtx_init(&txr->hn_txlist_spin, "hn txlist", NULL, MTX_SPIN);
+#endif
mtx_init(&txr->hn_tx_lock, "hn tx", NULL, MTX_DEF);
txr->hn_txdesc_cnt = HN_TX_DESC_CNT;
txr->hn_txdesc = malloc(sizeof(struct hn_txdesc) * txr->hn_txdesc_cnt,
M_NETVSC, M_WAITOK | M_ZERO);
+#ifndef HN_USE_TXDESC_BUFRING
SLIST_INIT(&txr->hn_txlist);
+#else
+ txr->hn_txdesc_br = buf_ring_alloc(txr->hn_txdesc_cnt, M_NETVSC,
+ M_WAITOK, &txr->hn_tx_lock);
+#endif
txr->hn_tx_taskq = sc->hn_tx_taskq;
TASK_INIT(&txr->hn_start_task, 0, hn_start_taskfunc, txr);
@@ -2158,7 +2188,11 @@
/* All set, put it to list */
txd->flags |= HN_TXD_FLAG_ONLIST;
+#ifndef HN_USE_TXDESC_BUFRING
SLIST_INSERT_HEAD(&txr->hn_txlist, txd, link);
+#else
+ buf_ring_enqueue(txr->hn_txdesc_br, txd);
+#endif
}
txr->hn_txdesc_avail = txr->hn_txdesc_cnt;
@@ -2191,35 +2225,47 @@
}
static void
+hn_txdesc_dmamap_destroy(struct hn_txdesc *txd)
+{
+ struct hn_tx_ring *txr = txd->txr;
+
+ KASSERT(txd->m == NULL, ("still has mbuf installed"));
+ KASSERT((txd->flags & HN_TXD_FLAG_DMAMAP) == 0, ("still dma mapped"));
+
+ bus_dmamap_unload(txr->hn_tx_rndis_dtag, txd->rndis_msg_dmap);
+ bus_dmamem_free(txr->hn_tx_rndis_dtag, txd->rndis_msg,
+ txd->rndis_msg_dmap);
+ bus_dmamap_destroy(txr->hn_tx_data_dtag, txd->data_dmap);
+}
+
+static void
hn_destroy_tx_ring(struct hn_tx_ring *txr)
{
struct hn_txdesc *txd;
if (txr->hn_txdesc == NULL)
return;
+#ifndef HN_USE_TXDESC_BUFRING
while ((txd = SLIST_FIRST(&txr->hn_txlist)) != NULL) {
- KASSERT(txd->m == NULL, ("still has mbuf installed"));
- KASSERT((txd->flags & HN_TXD_FLAG_DMAMAP) == 0,
- ("still dma mapped"));
SLIST_REMOVE_HEAD(&txr->hn_txlist, link);
-
- bus_dmamap_unload(txr->hn_tx_rndis_dtag,
- txd->rndis_msg_dmap);
- bus_dmamem_free(txr->hn_tx_rndis_dtag,
- txd->rndis_msg, txd->rndis_msg_dmap);
-
- bus_dmamap_destroy(txr->hn_tx_data_dtag, txd->data_dmap);
+ hn_txdesc_dmamap_destroy(txd);
}
+#else
+ while ((txd = buf_ring_dequeue_sc(txr->hn_txdesc_br)) != NULL)
+ hn_txdesc_dmamap_destroy(txd);
+#endif
if (txr->hn_tx_data_dtag != NULL)
bus_dma_tag_destroy(txr->hn_tx_data_dtag);
if (txr->hn_tx_rndis_dtag != NULL)
bus_dma_tag_destroy(txr->hn_tx_rndis_dtag);
free(txr->hn_txdesc, M_NETVSC);
txr->hn_txdesc = NULL;
+#ifndef HN_USE_TXDESC_BUFRING
mtx_destroy(&txr->hn_txlist_spin);
+#endif
mtx_destroy(&txr->hn_tx_lock);
}
diff --git a/sys/dev/hyperv/netvsc/hv_net_vsc.h b/sys/dev/hyperv/netvsc/hv_net_vsc.h
--- a/sys/dev/hyperv/netvsc/hv_net_vsc.h
+++ b/sys/dev/hyperv/netvsc/hv_net_vsc.h
@@ -58,6 +58,8 @@
#include <dev/hyperv/include/hyperv.h>
+#define HN_USE_TXDESC_BUFRING
+
MALLOC_DECLARE(M_NETVSC);
#define NVSP_INVALID_PROTOCOL_VERSION (0xFFFFFFFF)
@@ -990,8 +992,12 @@
hv_bool_uint8_t link_state;
} netvsc_device_info;
+#ifndef HN_USE_TXDESC_BUFRING
struct hn_txdesc;
SLIST_HEAD(hn_txdesc_list, hn_txdesc);
+#else
+struct buf_ring;
+#endif
struct hn_rx_ring {
struct lro_ctrl hn_lro;
@@ -1012,8 +1018,12 @@
#define HN_TRUST_HCSUM_UDP 0x0004
struct hn_tx_ring {
+#ifndef HN_USE_TXDESC_BUFRING
struct mtx hn_txlist_spin;
struct hn_txdesc_list hn_txlist;
+#else
+ struct buf_ring *hn_txdesc_br;
+#endif
int hn_txdesc_cnt;
int hn_txdesc_avail;
int hn_txeof;
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