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From: Jakub Kicinski <kuba@kernel.org>
To: Shenwei Wang <shenwei.wang@nxp.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Paolo Abeni <pabeni@redhat.com>, Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-stm32@st-md-mailman.stormreply.com, imx@lists.linux.dev,
	Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
Subject: Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode
Date: Wed, 4 Oct 2023 14:59:51 -0700	[thread overview]
Message-ID: <20231004145951.570a8ce4@kernel.org> (raw)
In-Reply-To: <20231004195442.414766-1-shenwei.wang@nxp.com>

On Wed,  4 Oct 2023 14:54:42 -0500 Shenwei Wang wrote:
> Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the
> DDR, AHB, and AXI buses based on system loading. If the dwmac interface
> in the driver does not request a HIGH frequency, it can significantly
> degrade performance when the system switches to a lower frequency to
> conserve power.
> 
> For example, on an i.MX8MQ EVK board, the throughput dropped to around
> 100Mbit/s on a 1Gbit connection:
> 
>     [ ID] Interval           Transfer     Bitrate
>     [  5]   0.00-10.00  sec   117 MBytes  97.9 Mbits/sec
> 
> However, throughput can return to expected levels after its driver requests
> the high frequency mode. Requesting high frequency in the dwmac driver is
> essential to maintain full throughput when the i.MX SoC adjusts bus speeds
> for power savings.

Oh, another one in one day :S Although this one feels much more like
a bug that escaped testing because testing didn't use power saving?
In any case, do you happen to have a user report you can mention here?
Quoting stable rules:

| Serious issues as reported by a user of a distribution kernel may also
| be considered if they fix a notable performance or interactivity
| issue. As these fixes are not as obvious and have a higher risk of a
| subtle regression they should only be submitted by a distribution
| kernel maintainer and include an addendum linking to a bugzilla entry
| if it exists and additional information on the user-visible impact.

And a Fixes tag would be good, please add.
-- 
pw-bot: cr

WARNING: multiple messages have this Message-ID (diff)
From: Jakub Kicinski <kuba@kernel.org>
To: Shenwei Wang <shenwei.wang@nxp.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Paolo Abeni <pabeni@redhat.com>, Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-stm32@st-md-mailman.stormreply.com, imx@lists.linux.dev,
	Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
Subject: Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode
Date: Wed, 4 Oct 2023 14:59:51 -0700	[thread overview]
Message-ID: <20231004145951.570a8ce4@kernel.org> (raw)
In-Reply-To: <20231004195442.414766-1-shenwei.wang@nxp.com>

On Wed,  4 Oct 2023 14:54:42 -0500 Shenwei Wang wrote:
> Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the
> DDR, AHB, and AXI buses based on system loading. If the dwmac interface
> in the driver does not request a HIGH frequency, it can significantly
> degrade performance when the system switches to a lower frequency to
> conserve power.
> 
> For example, on an i.MX8MQ EVK board, the throughput dropped to around
> 100Mbit/s on a 1Gbit connection:
> 
>     [ ID] Interval           Transfer     Bitrate
>     [  5]   0.00-10.00  sec   117 MBytes  97.9 Mbits/sec
> 
> However, throughput can return to expected levels after its driver requests
> the high frequency mode. Requesting high frequency in the dwmac driver is
> essential to maintain full throughput when the i.MX SoC adjusts bus speeds
> for power savings.

Oh, another one in one day :S Although this one feels much more like
a bug that escaped testing because testing didn't use power saving?
In any case, do you happen to have a user report you can mention here?
Quoting stable rules:

| Serious issues as reported by a user of a distribution kernel may also
| be considered if they fix a notable performance or interactivity
| issue. As these fixes are not as obvious and have a higher risk of a
| subtle regression they should only be submitted by a distribution
| kernel maintainer and include an addendum linking to a bugzilla entry
| if it exists and additional information on the user-visible impact.

And a Fixes tag would be good, please add.
-- 
pw-bot: cr

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2023-10-04 21:59 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-04 19:54 [PATCH net] net: stmmac: dwmac-imx: request high frequency mode Shenwei Wang
2023-10-04 19:54 ` Shenwei Wang
2023-10-04 20:00 ` Florian Fainelli
2023-10-04 20:00   ` Florian Fainelli
2023-10-04 20:16   ` Shenwei Wang
2023-10-04 20:16     ` Shenwei Wang
2023-10-04 21:59 ` Jakub Kicinski [this message]
2023-10-04 21:59   ` Jakub Kicinski
2023-10-05  3:09 ` Andrew Lunn
2023-10-05  3:09   ` Andrew Lunn
2023-10-05  6:28 ` [Linux-stm32] " Ahmad Fatoum
2023-10-05  6:28   ` Ahmad Fatoum
2023-10-05 14:56   ` [EXT] " Shenwei Wang
2023-10-05 14:56     ` Shenwei Wang
2023-10-05 10:42 ` kernel test robot
2023-10-05 10:42   ` kernel test robot
2023-10-24 16:16 ` kernel test robot
2023-10-24 16:16   ` kernel test robot

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