Author: luigi
Date: Wed Apr 11 16:11:08 2012
New Revision: 234140
URL: http://svn.freebsd.org/changeset/base/234140
Log:
A couple of changes related to ixgbe operation in netmap mode:
- add a sysctl, dev.netmap.ix_crcstrip, to control whether ixgbe should
strip the CRC on received frames. Defaults to 0, which keeps the CRC.
and improves performance when receiving min-sized (64-byte) frames.
This matters because min-sized frames is one of the standard
benchmarks for switches and routers, some chipsets seem to issue
read-modify-write cycles for PCIe transactions that are not a
full cache line, and a min-sized frame triggers the bug, resulting
in reduced throughput -- 9.7 instead of 14.88 Mpps -- and heavy
bus load.
- for the time being, always look for incoming packets on a select/poll
even if there has not been an interrupt in the meantime. This is
only a temporary workaround for a probable race condition in keeping
track of rx interrupts.
Add a couple of diagnostic vars to help studying the problem.
Modified:
head/sys/dev/netmap/ixgbe_netmap.h
head/sys/dev/netmap/netmap.c
Modified: head/sys/dev/netmap/ixgbe_netmap.h
==============================================================================
--- head/sys/dev/netmap/ixgbe_netmap.h Wed Apr 11 15:48:50 2012
(r234139)
+++ head/sys/dev/netmap/ixgbe_netmap.h Wed Apr 11 16:11:08 2012
(r234140)
@@ -49,6 +49,29 @@
*/
#include <dev/netmap/netmap_kern.h>
+/*
+ * ix_crcstrip: 0: keep CRC in rx frames (default), 1: strip it.
+ * During regular operations the CRC is stripped, but on some
+ * hardware reception of frames not multiple of 64 is slower,
+ * so using crcstrip=0 helps in benchmarks.
+ *
+ * ix_rx_miss, ix_rx_miss_bufs:
+ * count packets that might be missed due to lost interrupts.
+ *
+ * ix_use_dd
+ * use the dd bit for completed tx transmissions.
+ * This is tricky, much better to use TDH for now.
+ */
+SYSCTL_DECL(_dev_netmap);
+static int ix_rx_miss, ix_rx_miss_bufs, ix_use_dd, ix_crcstrip;
+SYSCTL_INT(_dev_netmap, OID_AUTO, ix_crcstrip,
+ CTLFLAG_RW, &ix_crcstrip, 0, "strip CRC on rx frames");
+SYSCTL_INT(_dev_netmap, OID_AUTO, ix_use_dd,
+ CTLFLAG_RW, &ix_use_dd, 0, "use dd instead of tdh to detect tx frames");
+SYSCTL_INT(_dev_netmap, OID_AUTO, ix_rx_miss,
+ CTLFLAG_RW, &ix_rx_miss, 0, "potentially missed rx intr");
+SYSCTL_INT(_dev_netmap, OID_AUTO, ix_rx_miss_bufs,
+ CTLFLAG_RW, &ix_rx_miss_bufs, 0, "potentially missed rx intr bufs");
/*
* wrapper to export locks to the generic netmap code.
@@ -82,6 +105,38 @@ ixgbe_netmap_lock_wrapper(struct ifnet *
}
+static void
+set_crcstrip(struct ixgbe_hw *hw, int onoff)
+{
+ /* crc stripping is set in two places:
+ * IXGBE_HLREG0 (left alone by the original driver)
+ * IXGBE_RDRXCTL (set by the original driver in
+ * ixgbe_setup_hw_rsc() called in init_locked.
+ * We disable the setting when netmap is compiled in).
+ * When netmap is compiled in we disabling IXGBE_RDRXCTL
+ * modifications of the IXGBE_RDRXCTL_CRCSTRIP bit, and
+ * instead update the state here.
+ */
+ uint32_t hl, rxc;
+
+ hl = IXGBE_READ_REG(hw, IXGBE_HLREG0);
+ rxc = IXGBE_READ_REG(hw, IXGBE_RDRXCTL);
+ /* hw requirements ... */
+ rxc &= ~IXGBE_RDRXCTL_RSCFRSTSIZE;
+ rxc |= IXGBE_RDRXCTL_RSCACKC;
+ if (onoff && !ix_crcstrip) {
+ /* keep the crc. Fast rx */
+ hl &= ~IXGBE_HLREG0_RXCRCSTRP;
+ rxc &= ~IXGBE_RDRXCTL_CRCSTRIP;
+ } else {
+ /* reset default mode */
+ hl |= IXGBE_HLREG0_RXCRCSTRP;
+ rxc |= IXGBE_RDRXCTL_CRCSTRIP;
+ }
+ IXGBE_WRITE_REG(hw, IXGBE_HLREG0, hl);
+ IXGBE_WRITE_REG(hw, IXGBE_RDRXCTL, rxc);
+}
+
/*
* Register/unregister. We are already under core lock.
* Only called on the first register or the last unregister.
@@ -101,6 +156,7 @@ ixgbe_netmap_reg(struct ifnet *ifp, int
/* Tell the stack that the interface is no longer active */
ifp->if_drv_flags &= ~(IFF_DRV_RUNNING | IFF_DRV_OACTIVE);
+ set_crcstrip(&adapter->hw, onoff);
if (onoff) { /* enable netmap mode */
ifp->if_capenable |= IFCAP_NETMAP;
@@ -125,6 +181,7 @@ fail:
/* initialize the card, this time in standard mode */
ixgbe_init_locked(adapter); /* also enables intr */
}
+ set_crcstrip(&adapter->hw, onoff);
return (error);
}
@@ -325,12 +382,26 @@ ring_reset:
* For the time being we use TDH, as we do it infrequently
* enough not to pose performance problems.
*/
+ if (ix_use_dd) {
+ struct ixgbe_legacy_tx_desc *txd =
+ (struct ixgbe_legacy_tx_desc *)txr->tx_base;
+
+ l = txr->next_to_clean;
+ k = netmap_idx_k2n(kring, kring->nr_hwcur);
+ delta = 0;
+ while (l != k &&
+ txd[l].upper.fields.status & IXGBE_TXD_STAT_DD) {
+ delta++;
+ l = (l == lim) ? 0 : l + 1;
+ }
+ } else {
l = IXGBE_READ_REG(&adapter->hw, IXGBE_TDH(ring_nr));
if (l >= kring->nkr_num_slots) { /* XXX can happen */
D("TDH wrap %d", l);
l -= kring->nkr_num_slots;
}
delta = l - txr->next_to_clean;
+ }
if (delta) {
/* some tx completed, increment avail */
if (delta < 0)
@@ -402,23 +473,29 @@ ixgbe_netmap_rxsync(struct ifnet *ifp, u
*
* rxr->next_to_check is set to 0 on a ring reinit
*/
- l = rxr->next_to_check;
- j = netmap_idx_n2k(kring, l);
-
if (netmap_no_pendintr || force_update) {
+ int crclen = ix_crcstrip ? 0 : 4;
+ l = rxr->next_to_check;
+ j = netmap_idx_n2k(kring, l);
+
for (n = 0; ; n++) {
union ixgbe_adv_rx_desc *curr = &rxr->rx_base[l];
uint32_t staterr = le32toh(curr->wb.upper.status_error);
if ((staterr & IXGBE_RXD_STAT_DD) == 0)
break;
- ring->slot[j].len = le16toh(curr->wb.upper.length);
+ ring->slot[j].len = le16toh(curr->wb.upper.length) -
crclen;
bus_dmamap_sync(rxr->ptag,
rxr->rx_buffers[l].pmap, BUS_DMASYNC_POSTREAD);
j = (j == lim) ? 0 : j + 1;
l = (l == lim) ? 0 : l + 1;
}
if (n) { /* update the state variables */
+ if (netmap_no_pendintr && !force_update) {
+ /* diagnostics */
+ ix_rx_miss ++;
+ ix_rx_miss_bufs += n;
+ }
rxr->next_to_check = l;
kring->nr_hwavail += n;
}
Modified: head/sys/dev/netmap/netmap.c
==============================================================================
--- head/sys/dev/netmap/netmap.c Wed Apr 11 15:48:50 2012
(r234139)
+++ head/sys/dev/netmap/netmap.c Wed Apr 11 16:11:08 2012
(r234140)
@@ -111,7 +111,7 @@ SYSCTL_INT(_dev_netmap, OID_AUTO, buf_si
CTLFLAG_RD, &netmap_buf_size, 0, "Size of packet buffers");
int netmap_mitigate = 1;
SYSCTL_INT(_dev_netmap, OID_AUTO, mitigate, CTLFLAG_RW, &netmap_mitigate, 0,
"");
-int netmap_no_pendintr;
+int netmap_no_pendintr = 1;
SYSCTL_INT(_dev_netmap, OID_AUTO, no_pendintr,
CTLFLAG_RW, &netmap_no_pendintr, 0, "Always look for new received
packets.");
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