From: Leon Romanovsky <leon@kernel.org>
To: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
David Miller <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>,
Eric Dumazet <edumazet@google.com>,
Realtek linux nic maintainers <nic_swsd@realtek.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH net-next v2 2/3] r8169: use new macro netif_subqueue_maybe_stop in rtl8169_start_xmit
Date: Sun, 16 Apr 2023 13:20:58 +0300 [thread overview]
Message-ID: <20230416102058.GC15386@unreal> (raw)
In-Reply-To: <69c2eec2-d82c-290a-d6ce-fba64afb32c6@gmail.com>
On Sat, Apr 15, 2023 at 09:22:11AM +0200, Heiner Kallweit wrote:
> Use new net core macro netif_subqueue_maybe_stop in the start_xmit path
> to simplify the code. Whilst at it, set the tx queue start threshold to
> twice the stop threshold. Before values were the same, resulting in
> stopping/starting the queue more often than needed.
>
> v2:
> - ring doorbell if queue was stopped
Please put changelog under "---" markup, below tags section.
Thanks
>
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
> drivers/net/ethernet/realtek/r8169_main.c | 39 +++++++----------------
> 1 file changed, 11 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 9f8357bbc..fff44d46b 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -30,6 +30,7 @@
> #include <linux/ipv6.h>
> #include <asm/unaligned.h>
> #include <net/ip6_checksum.h>
> +#include <net/netdev_queues.h>
>
> #include "r8169.h"
> #include "r8169_firmware.h"
> @@ -68,6 +69,8 @@
> #define NUM_RX_DESC 256 /* Number of Rx descriptor registers */
> #define R8169_TX_RING_BYTES (NUM_TX_DESC * sizeof(struct TxDesc))
> #define R8169_RX_RING_BYTES (NUM_RX_DESC * sizeof(struct RxDesc))
> +#define R8169_TX_STOP_THRS (MAX_SKB_FRAGS + 1)
> +#define R8169_TX_START_THRS (2 * R8169_TX_STOP_THRS)
>
> #define OCP_STD_PHY_BASE 0xa400
>
> @@ -4162,13 +4165,9 @@ static bool rtl8169_tso_csum_v2(struct rtl8169_private *tp,
> return true;
> }
>
> -static bool rtl_tx_slots_avail(struct rtl8169_private *tp)
> +static unsigned int rtl_tx_slots_avail(struct rtl8169_private *tp)
> {
> - unsigned int slots_avail = READ_ONCE(tp->dirty_tx) + NUM_TX_DESC
> - - READ_ONCE(tp->cur_tx);
> -
> - /* A skbuff with nr_frags needs nr_frags+1 entries in the tx queue */
> - return slots_avail > MAX_SKB_FRAGS;
> + return READ_ONCE(tp->dirty_tx) + NUM_TX_DESC - READ_ONCE(tp->cur_tx);
> }
>
> /* Versions RTL8102e and from RTL8168c onwards support csum_v2 */
> @@ -4245,27 +4244,10 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>
> WRITE_ONCE(tp->cur_tx, tp->cur_tx + frags + 1);
>
> - stop_queue = !rtl_tx_slots_avail(tp);
> - if (unlikely(stop_queue)) {
> - /* Avoid wrongly optimistic queue wake-up: rtl_tx thread must
> - * not miss a ring update when it notices a stopped queue.
> - */
> - smp_wmb();
> - netif_stop_queue(dev);
> - /* Sync with rtl_tx:
> - * - publish queue status and cur_tx ring index (write barrier)
> - * - refresh dirty_tx ring index (read barrier).
> - * May the current thread have a pessimistic view of the ring
> - * status and forget to wake up queue, a racing rtl_tx thread
> - * can't.
> - */
> - smp_mb__after_atomic();
> - if (rtl_tx_slots_avail(tp))
> - netif_start_queue(dev);
> - door_bell = true;
> - }
> -
> - if (door_bell)
> + stop_queue = !netif_subqueue_maybe_stop(dev, 0, rtl_tx_slots_avail(tp),
> + R8169_TX_STOP_THRS,
> + R8169_TX_START_THRS);
> + if (door_bell || stop_queue)
> rtl8169_doorbell(tp);
>
> return NETDEV_TX_OK;
> @@ -4400,7 +4382,8 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
> * ring status.
> */
> smp_store_mb(tp->dirty_tx, dirty_tx);
> - if (netif_queue_stopped(dev) && rtl_tx_slots_avail(tp))
> + if (netif_queue_stopped(dev) &&
> + rtl_tx_slots_avail(tp) >= R8169_TX_START_THRS)
> netif_wake_queue(dev);
> /*
> * 8168 hack: TxPoll requests are lost when the Tx packets are
> --
> 2.40.0
>
>
next prev parent reply other threads:[~2023-04-16 10:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-15 7:18 [PATCH net-next v2 0/3] r8169: use new macros from netdev_queues.h Heiner Kallweit
2023-04-15 7:20 ` [PATCH net-next v2 1/3] net: add macro netif_subqueue_completed_wake Heiner Kallweit
2023-04-15 7:22 ` [PATCH net-next v2 2/3] r8169: use new macro netif_subqueue_maybe_stop in rtl8169_start_xmit Heiner Kallweit
2023-04-16 10:20 ` Leon Romanovsky [this message]
2023-04-16 11:33 ` Heiner Kallweit
2023-04-16 13:24 ` Leon Romanovsky
2023-04-15 7:23 ` [PATCH net-next v2 3/3] r8169: use new macro netif_subqueue_completed_wake in the tx cleanup path Heiner Kallweit
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