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Date: Mon, 21 Mar 2022 17:07:55 +0100
From: Ansuel Smith <ansuelsmth@...il.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>,
Vivien Didelot <vivien.didelot@...il.com>,
Florian Fainelli <f.fainelli@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH v2] net: dsa: qca8k: pack driver struct and
improve cache use
On Thu, Mar 03, 2022 at 03:53:27AM +0200, Vladimir Oltean wrote:
> On Mon, Feb 28, 2022 at 12:04:08PM +0100, Ansuel Smith wrote:
> > Pack qca8k priv and other struct using pahole and set the first priv
> > struct entry to mgmt_master and mgmt_eth_data to speedup access.
> > While at it also rework pcs struct and move it qca8k_ports_config
> > following other configuration set for the cpu ports.
> >
> > Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> > ---
>
> How did you "pack" struct qca8k_priv exactly?
>
I'm trying to understand it too... also this was done basend on what
target?
> Before:
>
> struct qca8k_priv {
> u8 switch_id; /* 0 1 */
> u8 switch_revision; /* 1 1 */
> u8 mirror_rx; /* 2 1 */
> u8 mirror_tx; /* 3 1 */
> u8 lag_hash_mode; /* 4 1 */
> bool legacy_phy_port_mapping; /* 5 1 */
> struct qca8k_ports_config ports_config; /* 6 7 */
>
> /* XXX 3 bytes hole, try to pack */
>
> struct regmap * regmap; /* 16 8 */
> struct mii_bus * bus; /* 24 8 */
> struct ar8xxx_port_status port_sts[7]; /* 32 28 */
>
> /* XXX 4 bytes hole, try to pack */
>
> /* --- cacheline 1 boundary (64 bytes) --- */
> struct dsa_switch * ds; /* 64 8 */
> struct mutex reg_mutex; /* 72 160 */
> /* --- cacheline 3 boundary (192 bytes) was 40 bytes ago --- */
> struct device * dev; /* 232 8 */
> struct dsa_switch_ops ops; /* 240 864 */
> /* --- cacheline 17 boundary (1088 bytes) was 16 bytes ago --- */
> struct gpio_desc * reset_gpio; /* 1104 8 */
> unsigned int port_mtu[7]; /* 1112 28 */
>
> /* XXX 4 bytes hole, try to pack */
>
> struct net_device * mgmt_master; /* 1144 8 */
> /* --- cacheline 18 boundary (1152 bytes) --- */
> struct qca8k_mgmt_eth_data mgmt_eth_data; /* 1152 280 */
> /* --- cacheline 22 boundary (1408 bytes) was 24 bytes ago --- */
> struct qca8k_mib_eth_data mib_eth_data; /* 1432 272 */
> /* --- cacheline 26 boundary (1664 bytes) was 40 bytes ago --- */
> struct qca8k_mdio_cache mdio_cache; /* 1704 6 */
>
> /* XXX 2 bytes hole, try to pack */
>
> struct qca8k_pcs pcs_port_0; /* 1712 32 */
>
> /* XXX last struct has 4 bytes of padding */
>
> /* --- cacheline 27 boundary (1728 bytes) was 16 bytes ago --- */
> struct qca8k_pcs pcs_port_6; /* 1744 32 */
>
> /* XXX last struct has 4 bytes of padding */
>
> /* size: 1776, cachelines: 28, members: 22 */
> /* sum members: 1763, holes: 4, sum holes: 13 */
> /* paddings: 2, sum paddings: 8 */
> /* last cacheline: 48 bytes */
> };
>
> After:
>
> struct qca8k_priv {
> struct net_device * mgmt_master; /* 0 8 */
> struct qca8k_mgmt_eth_data mgmt_eth_data; /* 8 280 */
> /* --- cacheline 4 boundary (256 bytes) was 32 bytes ago --- */
> struct qca8k_mdio_cache mdio_cache; /* 288 6 */
> u8 switch_id; /* 294 1 */
> u8 switch_revision; /* 295 1 */
> u8 mirror_rx; /* 296 1 */
> u8 mirror_tx; /* 297 1 */
> u8 lag_hash_mode; /* 298 1 */
> bool legacy_phy_port_mapping; /* 299 1 */
>
> /* XXX 4 bytes hole, try to pack */
>
> struct qca8k_ports_config ports_config; /* 304 72 */
> /* --- cacheline 5 boundary (320 bytes) was 56 bytes ago --- */
> struct regmap * regmap; /* 376 8 */
> /* --- cacheline 6 boundary (384 bytes) --- */
> struct mii_bus * bus; /* 384 8 */
> struct ar8xxx_port_status port_sts[7]; /* 392 28 */
>
> /* XXX 4 bytes hole, try to pack */
>
> struct dsa_switch * ds; /* 424 8 */
> struct mutex reg_mutex; /* 432 160 */
> /* --- cacheline 9 boundary (576 bytes) was 16 bytes ago --- */
> struct device * dev; /* 592 8 */
> struct gpio_desc * reset_gpio; /* 600 8 */
> struct dsa_switch_ops ops; /* 608 864 */
> /* --- cacheline 23 boundary (1472 bytes) --- */
> struct qca8k_mib_eth_data mib_eth_data; /* 1472 280 */
>
> /* XXX last struct has 4 bytes of padding */
>
> /* --- cacheline 27 boundary (1728 bytes) was 24 bytes ago --- */
> unsigned int port_mtu[7]; /* 1752 28 */
>
> /* size: 1784, cachelines: 28, members: 20 */
> /* sum members: 1772, holes: 2, sum holes: 8 */
> /* padding: 4 */
> /* paddings: 1, sum paddings: 4 */
> /* last cacheline: 56 bytes */
> };
>
> 1776 vs 1784. That's... larger?!
>
> Also, struct qca8k_priv is so large because the "ops" member is a full
> copy of qca8k_switch_ops. I understand why commit db460c54b67f ("net:
> dsa: qca8k: extend slave-bus implementations") did this, but I wonder,
> is there no better way?
>
Actually from what I can see the struct can be improved in 2 way...
The ancient struct
ar8xxx_port_status port_sts[QCA8K_NUM_PORTS];
can be totally dropped as I can't see why we still need it.
The duplicated ops is funny. I could be very confused but why it's done
like that? Can't we modify directly the already defined one and drop
struct dsa_switch_ops ops; from qca8k_priv?
I mean is all of that to use priv->ops.phy_read instead of
priv->ds->ops.phy_read or even qca8k_switch_ops directly? o.o
Am I missing something?
> > drivers/net/dsa/qca8k.c | 8 ++++----
> > drivers/net/dsa/qca8k.h | 33 ++++++++++++++++-----------------
> > 2 files changed, 20 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> > index ee0dbf324268..8d059da5f0ca 100644
> > --- a/drivers/net/dsa/qca8k.c
> > +++ b/drivers/net/dsa/qca8k.c
> > @@ -1685,11 +1685,11 @@ qca8k_phylink_mac_select_pcs(struct dsa_switch *ds, int port,
> > case PHY_INTERFACE_MODE_1000BASEX:
> > switch (port) {
> > case 0:
> > - pcs = &priv->pcs_port_0.pcs;
> > + pcs = &priv->ports_config.qpcs[QCA8K_CPU_PORT0].pcs;
> > break;
> >
> > case 6:
> > - pcs = &priv->pcs_port_6.pcs;
> > + pcs = &priv->ports_config.qpcs[QCA8K_CPU_PORT6].pcs;
> > break;
> > }
> > break;
> > @@ -2889,8 +2889,8 @@ qca8k_setup(struct dsa_switch *ds)
> > if (ret)
> > return ret;
> >
> > - qca8k_setup_pcs(priv, &priv->pcs_port_0, 0);
> > - qca8k_setup_pcs(priv, &priv->pcs_port_6, 6);
> > + qca8k_setup_pcs(priv, &priv->ports_config.qpcs[QCA8K_CPU_PORT0], 0);
> > + qca8k_setup_pcs(priv, &priv->ports_config.qpcs[QCA8K_CPU_PORT6], 6);
> >
> > /* Make sure MAC06 is disabled */
> > ret = regmap_clear_bits(priv->regmap, QCA8K_REG_PORT0_PAD_CTRL,
> > diff --git a/drivers/net/dsa/qca8k.h b/drivers/net/dsa/qca8k.h
> > index f375627174c8..611dc2335dbe 100644
> > --- a/drivers/net/dsa/qca8k.h
> > +++ b/drivers/net/dsa/qca8k.h
> > @@ -341,18 +341,24 @@ enum {
> >
> > struct qca8k_mgmt_eth_data {
> > struct completion rw_done;
> > - struct mutex mutex; /* Enforce one mdio read/write at time */
> > + u32 data[4];
> > bool ack;
> > u32 seq;
> > - u32 data[4];
> > + struct mutex mutex; /* Enforce one mdio read/write at time */
> > };
> >
> > struct qca8k_mib_eth_data {
> > struct completion rw_done;
> > + u64 *data; /* pointer to ethtool data */
> > + u8 req_port;
> > struct mutex mutex; /* Process one command at time */
> > refcount_t port_parsed; /* Counter to track parsed port */
> > - u8 req_port;
> > - u64 *data; /* pointer to ethtool data */
> > +};
> > +
> > +struct qca8k_pcs {
> > + struct phylink_pcs pcs;
> > + struct qca8k_priv *priv;
> > + int port;
> > };
> >
> > struct qca8k_ports_config {
> > @@ -361,6 +367,7 @@ struct qca8k_ports_config {
> > bool sgmii_enable_pll;
> > u8 rgmii_rx_delay[QCA8K_NUM_CPU_PORTS]; /* 0: CPU port0, 1: CPU port6 */
> > u8 rgmii_tx_delay[QCA8K_NUM_CPU_PORTS]; /* 0: CPU port0, 1: CPU port6 */
> > + struct qca8k_pcs qpcs[QCA8K_NUM_CPU_PORTS];
> > };
> >
> > struct qca8k_mdio_cache {
> > @@ -376,13 +383,10 @@ struct qca8k_mdio_cache {
> > u16 hi;
> > };
> >
> > -struct qca8k_pcs {
> > - struct phylink_pcs pcs;
> > - struct qca8k_priv *priv;
> > - int port;
> > -};
> > -
> > struct qca8k_priv {
> > + struct net_device *mgmt_master; /* Track if mdio/mib Ethernet is available */
> > + struct qca8k_mgmt_eth_data mgmt_eth_data;
> > + struct qca8k_mdio_cache mdio_cache;
> > u8 switch_id;
> > u8 switch_revision;
> > u8 mirror_rx;
> > @@ -396,15 +400,10 @@ struct qca8k_priv {
> > struct dsa_switch *ds;
> > struct mutex reg_mutex;
> > struct device *dev;
> > - struct dsa_switch_ops ops;
> > struct gpio_desc *reset_gpio;
> > - unsigned int port_mtu[QCA8K_NUM_PORTS];
> > - struct net_device *mgmt_master; /* Track if mdio/mib Ethernet is available */
> > - struct qca8k_mgmt_eth_data mgmt_eth_data;
> > + struct dsa_switch_ops ops;
> > struct qca8k_mib_eth_data mib_eth_data;
> > - struct qca8k_mdio_cache mdio_cache;
> > - struct qca8k_pcs pcs_port_0;
> > - struct qca8k_pcs pcs_port_6;
> > + unsigned int port_mtu[QCA8K_NUM_PORTS];
> > };
> >
> > struct qca8k_mib_desc {
> > --
> > 2.34.1
> >
>
--
Ansuel
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