From: Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Markus Schneider-Pargmann <msp@baylibre.com>,
Chandrasekar Ramakrishnan <rcsekar@samsung.com>,
Wolfgang Grandegger <wg@grandegger.com>,
linux-can@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/15] can: m_can: Wakeup net queue once tx was issued
Date: Wed, 14 Dec 2022 19:15:25 +0900 [thread overview]
Message-ID: <CAMZ6RqLAZNj9dm_frbKExHK8AYDj9D0rX_9=c8_wk9kFrO-srw@mail.gmail.com> (raw)
In-Reply-To: <20221214092201.xpb3rnwp5rtvrpkr@pengutronix.de>
On Wed. 14 Dec. 2022 at 18:28, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
> On 14.12.2022 10:18:20, Marc Kleine-Budde wrote:
> > On 14.12.2022 10:14:06, Markus Schneider-Pargmann wrote:
> > > Hi Marc,
> > >
> > > On Wed, Nov 30, 2022 at 06:21:00PM +0100, Marc Kleine-Budde wrote:
> > > > On 16.11.2022 21:52:55, Markus Schneider-Pargmann wrote:
> > > > > Currently the driver waits to wakeup the queue until the interrupt for
> > > > > the transmit event is received and acknowledged. If we want to use the
> > > > > hardware FIFO, this is too late.
> > > > >
> > > > > Instead release the queue as soon as the transmit was transferred into
> > > > > the hardware FIFO. We are then ready for the next transmit to be
> > > > > transferred.
> > > >
> > > > If you want to really speed up the TX path, remove the worker and use
> > > > the spi_async() API from the xmit callback, see mcp251xfd_start_xmit().
> > > >
> > > > Extra bonus if you implement xmit_more() and transfer more than 1 skb
> > > > per SPI transfer.
> > >
> > > Just a quick question here, I mplemented a xmit_more() call and I am
> > > testing it right now, but it always returns false even under high
> > > pressure. The device has a txqueuelen set to 1000. Do I need to turn
> > > some other knob for this to work?
I was the first to use BQL in a CAN driver. It also took me time to
first figure out the existence of xmit_more() and even more to
understand how to make it so that it would return true.
> > AFAIK you need BQL support: see 0084e298acfe ("can: mcp251xfd: add BQL support").
> >
> > The etas_es58x driver implements xmit_more(), I added the Author Vincent
> > on Cc.
>
> Have a look at netdev_queue_set_dql_min_limit() in the etas driver.
The functions you need are the netdev_send_queue() and the
netdev_complete_queue():
https://elixir.bootlin.com/linux/latest/source/include/linux/netdevice.h#L3424
For CAN, you probably want to have a look to can_skb_get_frame_len().
https://elixir.bootlin.com/linux/latest/source/include/linux/can/length.h#L166
The netdev_queue_set_dql_min_limit() gives hints by setting a minimum
value for BQL. It is optional (and as of today I am the only user of
it).
Yours sincerely,
Vincent Mailhol
next prev parent reply other threads:[~2022-12-14 10:15 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-16 20:52 [PATCH 00/15] can: m_can: Optimizations for tcan and peripheral chips Markus Schneider-Pargmann
2022-11-16 20:52 ` [PATCH 01/15] can: m_can: Eliminate double read of TXFQS in tx_handler Markus Schneider-Pargmann
2022-11-16 20:52 ` [PATCH 02/15] can: m_can: Wakeup net queue once tx was issued Markus Schneider-Pargmann
2022-11-30 17:21 ` Marc Kleine-Budde
2022-12-01 8:43 ` Markus Schneider-Pargmann
2022-12-01 9:16 ` Marc Kleine-Budde
2022-12-01 16:49 ` Markus Schneider-Pargmann
2022-12-02 9:16 ` Marc Kleine-Budde
2022-12-14 9:14 ` Markus Schneider-Pargmann
2022-12-14 9:18 ` Marc Kleine-Budde
2022-12-14 9:22 ` Marc Kleine-Budde
2022-12-14 10:15 ` Vincent MAILHOL [this message]
2022-12-14 10:35 ` Markus Schneider-Pargmann
2022-12-15 9:31 ` Markus Schneider-Pargmann
2022-12-16 4:40 ` Vincent MAILHOL
2022-12-14 10:18 ` Markus Schneider-Pargmann
2022-12-02 13:53 ` Marc Kleine-Budde
2022-11-16 20:52 ` [PATCH 03/15] can: m_can: Cache tx putidx and transmits in flight Markus Schneider-Pargmann
2022-12-01 11:14 ` Marc Kleine-Budde
2022-12-02 8:37 ` Markus Schneider-Pargmann
2022-12-02 14:46 ` Marc Kleine-Budde
2022-12-13 17:13 ` Markus Schneider-Pargmann
2022-12-13 19:17 ` Marc Kleine-Budde
2022-12-14 8:32 ` Markus Schneider-Pargmann
2022-11-16 20:52 ` [PATCH 04/15] can: m_can: Use transmit event FIFO watermark level interrupt Markus Schneider-Pargmann
2022-11-30 17:17 ` Marc Kleine-Budde
2022-12-01 8:25 ` Markus Schneider-Pargmann
2022-12-01 9:05 ` Marc Kleine-Budde
2022-12-01 10:12 ` Markus Schneider-Pargmann
2022-12-01 11:00 ` Marc Kleine-Budde
2022-12-01 16:59 ` Markus Schneider-Pargmann
2022-12-02 9:23 ` Marc Kleine-Budde
2022-12-02 9:43 ` Markus Schneider-Pargmann
2022-12-02 14:03 ` Marc Kleine-Budde
2022-12-13 17:19 ` Markus Schneider-Pargmann
2022-12-13 19:18 ` Marc Kleine-Budde
2022-11-16 20:52 ` [PATCH 05/15] can: m_can: Disable unused interrupts Markus Schneider-Pargmann
2022-11-16 20:52 ` [PATCH 06/15] can: m_can: Avoid reading irqstatus twice Markus Schneider-Pargmann
2022-11-16 20:53 ` [PATCH 07/15] can: m_can: Read register PSR only on error Markus Schneider-Pargmann
2022-11-16 20:53 ` [PATCH 08/15] can: m_can: Count TXE FIFO getidx in the driver Markus Schneider-Pargmann
2022-11-16 20:53 ` [PATCH 09/15] can: m_can: Count read getindex " Markus Schneider-Pargmann
2022-11-16 20:53 ` [PATCH 10/15] can: m_can: Batch acknowledge rx fifo Markus Schneider-Pargmann
2022-11-16 20:53 ` [PATCH 11/15] can: m_can: Batch acknowledge transmit events Markus Schneider-Pargmann
2022-11-16 20:53 ` [PATCH 12/15] can: tcan4x5x: Remove invalid write in clear_interrupts Markus Schneider-Pargmann
2022-12-02 14:17 ` Marc Kleine-Budde
2022-11-16 20:53 ` [PATCH 13/15] can: tcan4x5x: Fix use of register error status mask Markus Schneider-Pargmann
2022-12-02 14:19 ` Marc Kleine-Budde
2022-11-16 20:53 ` [PATCH 14/15] can: tcan4x5x: Fix register range of first block Markus Schneider-Pargmann
2022-12-02 14:28 ` Marc Kleine-Budde
2022-12-05 9:30 ` Markus Schneider-Pargmann
2022-12-05 9:44 ` Marc Kleine-Budde
2022-12-05 9:55 ` Markus Schneider-Pargmann
2022-11-16 20:53 ` [PATCH 15/15] can: tcan4x5x: Specify separate read/write ranges Markus Schneider-Pargmann
2022-12-02 14:03 ` [PATCH 00/15] can: m_can: Optimizations for tcan and peripheral chips Marc Kleine-Budde
2022-12-05 9:09 ` Markus Schneider-Pargmann
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