linux-kernel - Re: [RFC PATCH 0/1] vmxnet3: Adjust maximum Rx ring buffer size

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Message-ID: <031eafb1-4fa6-4008-92c3-0f6ecec7ce63@broadcom.com>
Date: Mon, 6 Jan 2025 15:51:10 -0800
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Jakub Kicinski <kuba@...nel.org>, Aaron Tomlin <atomlin@...mlin.com>
Cc: ronak.doshi@...adcom.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com,
 bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/1] vmxnet3: Adjust maximum Rx ring buffer size

On 1/6/25 15:47, 'Jakub Kicinski' via BCM-KERNEL-FEEDBACK-LIST,PDL wrote:
> On Sun,  5 Jan 2025 21:30:35 +0000 Aaron Tomlin wrote:
>> I managed to trigger the MAX_PAGE_ORDER warning in the context of function
>> __alloc_pages_noprof() with /usr/sbin/ethtool --set-ring rx 4096 rx-mini
>> 2048 [devname]' using the maximum supported Ring 0 and Rx ring buffer size.
>> Admittedly this was under the stock Linux kernel-4.18.0-477.27.1.el8_8
>> whereby CONFIG_CMA is not enabled. I think it does not make sense to
>> attempt a large memory allocation request for physically contiguous memory,
>> to hold the Rx Data ring that could exceed the maximum page-order supported
>> by the system.
> 
> I think CMA should be a bit orthogonal to the warning.
> 
> Off the top of my head the usual way to solve the warning is to add
> __GFP_NOWARN to the allocations which trigger it. And then handle
> the error gracefully.

That IMHO should really be the default for any driver that calls 
__netdev_alloc_skb() under the hood, we should not really have to 
specify __GFP_NOWARN, rather if people want it, they should specify it.
-- 
Florian