lkml.org 
[lkml]   [2021]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH v2 3/6] net: ocelot: pre-compute injection frame header content
    Date
    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?

    > 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 Gaps
    > diff --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
    >
    \
     
     \ /
      Last update: 2021-11-03 13:39    [W:5.373 / U:0.276 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site