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Message-ID: <20240201122705.GA530335@kernel.org>
Date: Thu, 1 Feb 2024 13:27:05 +0100
From: Simon Horman <horms@...nel.org>
To: darinzon@...zon.com
Cc: "Nelson, Shannon" <shannon.nelson@....com>,
David Miller <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
"Woodhouse, David" <dwmw@...zon.com>,
"Machulsky, Zorik" <zorik@...zon.com>,
"Matushevsky, Alexander" <matua@...zon.com>,
Saeed Bshara <saeedb@...zon.com>, "Wilson, Matt" <msw@...zon.com>,
"Liguori, Anthony" <aliguori@...zon.com>,
"Bshara, Nafea" <nafea@...zon.com>,
"Belgazal, Netanel" <netanel@...zon.com>,
"Saidi, Ali" <alisaidi@...zon.com>,
"Herrenschmidt, Benjamin" <benh@...zon.com>,
"Kiyanovski, Arthur" <akiyano@...zon.com>,
"Dagan, Noam" <ndagan@...zon.com>,
"Agroskin, Shay" <shayagr@...zon.com>,
"Itzko, Shahar" <itzko@...zon.com>,
"Abboud, Osama" <osamaabb@...zon.com>,
"Ostrovsky, Evgeny" <evostrov@...zon.com>,
"Tabachnik, Ofir" <ofirt@...zon.com>,
"Koler, Nati" <nkoler@...zon.com>
Subject: Re: [PATCH v2 net-next 07/11] net: ena: Add more information on TX
timeouts
On Tue, Jan 30, 2024 at 09:53:49AM +0000, darinzon@...zon.com wrote:
> From: David Arinzon <darinzon@...zon.com>
>
> The function responsible for polling TX completions might not receive
> the CPU resources it needs due to higher priority tasks running on the
> requested core.
>
> The driver might not be able to recognize such cases, but it can use its
> state to suspect that they happened. If both conditions are met:
>
> - napi hasn't been executed more than the TX completion timeout value
> - napi is scheduled (meaning that we've received an interrupt)
>
> Then it's more likely that the napi handler isn't scheduled because of
> an overloaded CPU.
> It was decided that for this case, the driver would wait twice as long
> as the regular timeout before scheduling a reset.
> The driver uses ENA_REGS_RESET_SUSPECTED_POLL_STARVATION reset reason to
> indicate this case to the device.
>
> This patch also adds more information to the ena_tx_timeout() callback.
> This function is called by the kernel when it detects that a specific TX
> queue has been closed for too long.
>
> Signed-off-by: Shay Agroskin <shayagr@...zon.com>
> Signed-off-by: David Arinzon <darinzon@...zon.com>
> ---
> drivers/net/ethernet/amazon/ena/ena_netdev.c | 77 +++++++++++++++----
> .../net/ethernet/amazon/ena/ena_regs_defs.h | 1 +
> 2 files changed, 64 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> index 18acb76..ae9291b 100644
> --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
> +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> @@ -47,19 +47,44 @@ static int ena_restore_device(struct ena_adapter *adapter);
>
> static void ena_tx_timeout(struct net_device *dev, unsigned int txqueue)
> {
> + enum ena_regs_reset_reason_types reset_reason = ENA_REGS_RESET_OS_NETDEV_WD;
> struct ena_adapter *adapter = netdev_priv(dev);
> + unsigned int time_since_last_napi, threshold;
> + struct ena_ring *tx_ring;
> + int napi_scheduled;
> +
> + if (txqueue >= adapter->num_io_queues) {
> + netdev_err(dev, "TX timeout on invalid queue %u\n", txqueue);
> + goto schedule_reset;
> + }
> +
> + threshold = jiffies_to_usecs(dev->watchdog_timeo);
> + tx_ring = &adapter->tx_ring[txqueue];
> +
> + time_since_last_napi = jiffies_to_usecs(jiffies - tx_ring->tx_stats.last_napi_jiffies);
> + napi_scheduled = !!(tx_ring->napi->state & NAPIF_STATE_SCHED);
>
> + netdev_err(dev,
> + "TX q %d is paused for too long (threshold %u). Time since last napi %u usec. napi scheduled: %d\n",
> + txqueue,
> + threshold,
> + time_since_last_napi,
> + napi_scheduled);
> +
> + if (threshold < time_since_last_napi && napi_scheduled) {
> + netdev_err(dev,
> + "napi handler hasn't been called for a long time but is scheduled\n");
> + reset_reason = ENA_REGS_RESET_SUSPECTED_POLL_STARVATION;
Hi David,
a nit from my side: the line above is indented one tab-stop too many.
No need to respin just for this AFAIC.
> + }
> +schedule_reset:
> /* Change the state of the device to trigger reset
> * Check that we are not in the middle or a trigger already
> */
> -
> if (test_and_set_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags))
> return;
>
> - ena_reset_device(adapter, ENA_REGS_RESET_OS_NETDEV_WD);
> + ena_reset_device(adapter, reset_reason);
> ena_increase_stat(&adapter->dev_stats.tx_timeout, 1, &adapter->syncp);
> -
> - netif_err(adapter, tx_err, dev, "Transmit time out\n");
> }
>
...
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