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

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Message-ID: <20250106154741.23902c1a@kernel.org>
Date: Mon, 6 Jan 2025 15:47:41 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: 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 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.