Re: [PATCH v2 3/6] net: ocelot: pre-compute injection frame header content
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: 2021-11-03 12:38:19
Also in:
lkml, netdev
On Wed, Nov 03, 2021 at 10:19:40AM +0100, Clément Léger wrote:
IFH preparation can take quite some time on slow processors (up to 5% in a iperf3 test for instance). In order to reduce the cost of this preparation, pre-compute IFH since most of the parameters are fixed per port. Only rew_op and vlan tag will be set when sending if different than 0. This allows to remove entirely the calls to packing() with basic usage. In the same time, export this function that will be used by FDMA. Signed-off-by: Clément Léger <clement.leger@bootlin.com> ---
Honestly, this feels a bit cheap/gimmicky, and not really the
fundamental thing to address. In my testing of a similar idea (see
commits 67c2404922c2 ("net: dsa: felix: create a template for the DSA
tags on xmit") and then 7c4bb540e917 ("net: dsa: tag_ocelot: create
separate tagger for Seville"), the net difference is not that stark,
considering that now you need to access one more memory region which you
did not need before, do a memcpy, and then patch the IFH anyway for the
non-constant stuff.
Certainly, for the calls to ocelot_port_inject_frame() from DSA, I would
prefer not having this pre-computed IFH.
Could you provide some before/after performance numbers and perf counters?
quoted hunk ↗ jump to hunk
drivers/net/ethernet/mscc/ocelot.c | 23 ++++++++++++++++++----- include/soc/mscc/ocelot.h | 5 +++++ 2 files changed, 23 insertions(+), 5 deletions(-)diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c index e6c18b598d5c..97693772595b 100644 --- a/drivers/net/ethernet/mscc/ocelot.c +++ b/drivers/net/ethernet/mscc/ocelot.c@@ -1076,20 +1076,29 @@ bool ocelot_can_inject(struct ocelot *ocelot, int grp) } EXPORT_SYMBOL(ocelot_can_inject); +void ocelot_ifh_port_set(void *ifh, struct ocelot_port *port, u32 rew_op, + u32 vlan_tag) +{ + memcpy(ifh, port->ifh, OCELOT_TAG_LEN); + + if (vlan_tag) + ocelot_ifh_set_vlan_tci(ifh, vlan_tag); + if (rew_op) + ocelot_ifh_set_rew_op(ifh, rew_op); +} +EXPORT_SYMBOL(ocelot_ifh_port_set); + void ocelot_port_inject_frame(struct ocelot *ocelot, int port, int grp, u32 rew_op, struct sk_buff *skb) { + struct ocelot_port *port_s = ocelot->ports[port]; u32 ifh[OCELOT_TAG_LEN / 4] = {0}; unsigned int i, count, last; ocelot_write_rix(ocelot, QS_INJ_CTRL_GAP_SIZE(1) | QS_INJ_CTRL_SOF, QS_INJ_CTRL, grp); - ocelot_ifh_set_bypass(ifh, 1); - ocelot_ifh_set_dest(ifh, BIT_ULL(port)); - ocelot_ifh_set_tag_type(ifh, IFH_TAG_TYPE_C); - ocelot_ifh_set_vlan_tci(ifh, skb_vlan_tag_get(skb)); - ocelot_ifh_set_rew_op(ifh, rew_op); + ocelot_ifh_port_set(ifh, port_s, rew_op, skb_vlan_tag_get(skb)); for (i = 0; i < OCELOT_TAG_LEN / 4; i++) ocelot_write_rix(ocelot, ifh[i], QS_INJ_WR, grp);@@ -2128,6 +2137,10 @@ void ocelot_init_port(struct ocelot *ocelot, int port) skb_queue_head_init(&ocelot_port->tx_skbs); + ocelot_ifh_set_bypass(ocelot_port->ifh, 1); + ocelot_ifh_set_dest(ocelot_port->ifh, BIT_ULL(port)); + ocelot_ifh_set_tag_type(ocelot_port->ifh, IFH_TAG_TYPE_C); + /* Basic L2 initialization */ /* Set MAC IFG Gapsdiff --git a/include/soc/mscc/ocelot.h b/include/soc/mscc/ocelot.h index fef3a36b0210..b3381c90ff3e 100644 --- a/include/soc/mscc/ocelot.h +++ b/include/soc/mscc/ocelot.h@@ -6,6 +6,7 @@ #define _SOC_MSCC_OCELOT_H #include <linux/ptp_clock_kernel.h> +#include <linux/dsa/ocelot.h> #include <linux/net_tstamp.h> #include <linux/if_vlan.h> #include <linux/regmap.h>@@ -623,6 +624,8 @@ struct ocelot_port { struct net_device *bridge; u8 stp_state; + + u8 ifh[OCELOT_TAG_LEN]; }; struct ocelot {@@ -754,6 +757,8 @@ void __ocelot_target_write_ix(struct ocelot *ocelot, enum ocelot_target target, bool ocelot_can_inject(struct ocelot *ocelot, int grp); void ocelot_port_inject_frame(struct ocelot *ocelot, int port, int grp, u32 rew_op, struct sk_buff *skb); +void ocelot_ifh_port_set(void *ifh, struct ocelot_port *port, u32 rew_op, + u32 vlan_tag); int ocelot_xtr_poll_frame(struct ocelot *ocelot, int grp, struct sk_buff **skb); void ocelot_drain_cpu_queue(struct ocelot *ocelot, int grp);-- 2.33.0