From: Florian Fainelli <f.fainelli@gmail.com>
To: Vladimir Oltean <olteanv@gmail.com>, netdev@vger.kernel.org
Cc: alexandre.belloni@bootlin.com, andrew@lunn.ch,
vivien.didelot@gmail.com, alexandru.marginean@nxp.com,
claudiu.manoil@nxp.com, xiaoliang.yang_1@nxp.com,
hongbo.wang@nxp.com, kuba@kernel.org, jiri@resnulli.us,
idosch@idosch.org, UNGLinuxDriver@microchip.com
Subject: Re: [PATCH v3 net-next 09/10] net: mscc: ocelot: initialize watermarks to sane defaults
Date: Fri, 8 Jan 2021 19:59:36 -0800 [thread overview]
Message-ID: <84d6345b-f197-27b5-6201-f678c03ec259@gmail.com> (raw)
In-Reply-To: <20210108175950.484854-10-olteanv@gmail.com>
On 1/8/2021 9:59 AM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
>
> This is meant to be a gentle introduction into the world of watermarks
> on ocelot. The code is placed in ocelot_devlink.c because it will be
> integrated with devlink, even if it isn't right now.
>
> My first step was intended to be to replicate the default configuration
> of the congestion watermarks programatically, since they are now going
> to be tuned by the user.
>
> But after studying and understanding through trial and error how they
> work, I now believe that the configuration used out of reset does not do
> justice to the word "reservation", since the sum of all reservations
> exceeds the total amount of resources (otherwise said, all reservations
> cannot be fulfilled at the same time, which means that, contrary to the
> reference manual, they don't guarantee anything).
>
> As an example, here's a dump of the reservation watermarks for frame
> buffers, for port 0 (for brevity, the ports 1-6 were omitted, but they
> have the same configuration):
>
> BUF_Q_RSRV_I(port 0, prio 0) = max 3000 bytes
> BUF_Q_RSRV_I(port 0, prio 1) = max 3000 bytes
> BUF_Q_RSRV_I(port 0, prio 2) = max 3000 bytes
> BUF_Q_RSRV_I(port 0, prio 3) = max 3000 bytes
> BUF_Q_RSRV_I(port 0, prio 4) = max 3000 bytes
> BUF_Q_RSRV_I(port 0, prio 5) = max 3000 bytes
> BUF_Q_RSRV_I(port 0, prio 6) = max 3000 bytes
> BUF_Q_RSRV_I(port 0, prio 7) = max 3000 bytes
>
> Otherwise said, every port-tc has an ingress reservation of 3000 bytes,
> and there are 7 ports in VSC9959 Felix (6 user ports and 1 CPU port).
> Concentrating only on the ingress reservations, there are, in total,
> 8 [traffic classes] x 7 [ports] x 3000 [bytes] = 168,000 bytes of memory
> reserved on ingress.
> But, surprise, Felix only has 128 KB of packet buffer in total...
> A similar thing happens with Seville, which has a larger packet buffer,
> but also more ports, and the default configuration is also overcommitted.
>
> This patch disables the (apparently) bogus reservations and moves all
> resources to the shared area. This way, real reservations can be set up
> by the user, using devlink-sb.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
--
Florian
next prev parent reply other threads:[~2021-01-09 4:04 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-08 17:59 [PATCH v3 net-next 00/10] Configuring congestion watermarks on ocelot switch using devlink-sb Vladimir Oltean
2021-01-08 17:59 ` [PATCH v3 net-next 01/10] net: mscc: ocelot: auto-detect packet buffer size and number of frame references Vladimir Oltean
2021-01-08 18:30 ` Florian Fainelli
2021-01-08 17:59 ` [PATCH v3 net-next 02/10] net: mscc: ocelot: add ops for decoding watermark threshold and occupancy Vladimir Oltean
2021-01-08 18:30 ` Florian Fainelli
2021-01-10 1:20 ` Jakub Kicinski
2021-01-11 16:53 ` Vladimir Oltean
2021-01-11 19:10 ` Jakub Kicinski
2021-01-08 17:59 ` [PATCH v3 net-next 03/10] net: dsa: add ops for devlink-sb Vladimir Oltean
2021-01-08 18:20 ` Andrew Lunn
2021-01-08 18:31 ` Florian Fainelli
2021-01-08 17:59 ` [PATCH v3 net-next 04/10] net: dsa: felix: reindent struct dsa_switch_ops Vladimir Oltean
2021-01-08 18:33 ` Florian Fainelli
2021-01-10 1:24 ` Jakub Kicinski
2021-01-11 17:01 ` Vladimir Oltean
2021-01-11 19:12 ` Jakub Kicinski
2021-01-08 17:59 ` [PATCH v3 net-next 05/10] net: dsa: felix: perform teardown in reverse order of setup Vladimir Oltean
2021-01-08 18:34 ` Florian Fainelli
2021-01-08 17:59 ` [PATCH v3 net-next 06/10] net: mscc: ocelot: export NUM_TC constant from felix to common switch lib Vladimir Oltean
2021-01-08 18:34 ` Florian Fainelli
2021-01-08 17:59 ` [PATCH v3 net-next 07/10] net: mscc: ocelot: delete unused ocelot_set_cpu_port prototype Vladimir Oltean
2021-01-08 18:35 ` Florian Fainelli
2021-01-08 17:59 ` [PATCH v3 net-next 08/10] net: mscc: ocelot: register devlink ports Vladimir Oltean
2021-01-08 18:36 ` Florian Fainelli
2021-01-10 1:44 ` Jakub Kicinski
2021-01-11 17:13 ` Vladimir Oltean
2021-01-11 19:19 ` Jakub Kicinski
2021-01-14 10:34 ` Vladimir Oltean
2021-01-14 16:44 ` Jakub Kicinski
2021-01-15 17:11 ` Renaming interfaces that are up (Was "Re: [PATCH v3 net-next 08/10] net: mscc: ocelot: register devlink") ports Vladimir Oltean
2021-01-15 19:54 ` Vladimir Oltean
2021-01-10 2:01 ` [PATCH v3 net-next 08/10] net: mscc: ocelot: register devlink ports Jakub Kicinski
2021-01-08 17:59 ` [PATCH v3 net-next 09/10] net: mscc: ocelot: initialize watermarks to sane defaults Vladimir Oltean
2021-01-09 3:59 ` Florian Fainelli [this message]
2021-01-08 17:59 ` [PATCH v3 net-next 10/10] net: mscc: ocelot: configure watermarks using devlink-sb Vladimir Oltean
2021-01-09 4:03 ` Florian Fainelli
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