Re: [PATCH] vmxnet3: Suppress page allocation warning for massive Rx Data ring

[Aaron Tomlin]

On Tue, Feb 24, 2026 at 05:02:55PM +0800, Jijie Shao wrote:
> 
> on 2026/2/23 22:56, Aaron Tomlin wrote:
> > The vmxnet3 driver supports an Rx Data ring (rx-mini) to optimise the
> > processing of small packets. The size of this ring's DMA-coherent memory
> > allocation is determined by the product of the primary Rx ring size and
> > the data ring descriptor size:
> > 
> >      sz = rq->rx_ring[0].size * rq->data_ring.desc_size;
> > 
> > When a user configures the maximum supported parameters via ethtool
> > (rx_ring[0].size = 4096, data_ring.desc_size = 2048), the required
> > contiguous memory allocation reaches 8 MB (8,388,608 bytes).
> > 
> > In environments lacking Contiguous Memory Allocator (CMA),
> > dma_alloc_coherent() falls back to the standard zone buddy allocator. An
> > 8 MB allocation translates to a page order of 11, which strictly exceeds
> > the default MAX_PAGE_ORDER (10) on most architectures.
> > 
> > Consequently, __alloc_pages_noprof() catches the oversize request and
> > triggers a loud kernel warning stack trace:
> > 
> >      WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)
> > 
> > This warning is unnecessary and alarming to system administrators because
> > the vmxnet3 driver already handles this allocation failure gracefully.
> > If dma_alloc_coherent() returns NULL, the driver safely disables the
> > Rx Data ring (adapter->rxdataring_enabled = false) and falls back to
> > standard, streaming DMA packet processing.
> > 
> > To resolve this, append the __GFP_NOWARN flag to the dma_alloc_coherent()
> > gfp_mask. This instructs the page allocator to silently fail the
> > allocation if it exceeds order limits or memory is too fragmented,
> > preventing the spurious warning stack trace.
> 
> This seems to be a suitable solution.
> I see many drivers appending the __GFP_NOWARN flag to the dma_alloc_coherent() gfp_mask.
> 
> Reviewed-by: Jijie Shao <shaojijie@xxxxxxxxxx>

Hi Jijie,

Thank you for your feedback.

> > -					   GFP_KERNEL);
> > +					   GFP_KERNEL | __GFP_NOWARN);
> >   		if (!rq->data_ring.base) {
> >   			netdev_err(adapter->netdev,
> > -				   "rx data ring will be disabled\n");
> > +				   "Failed to allocate %zu bytes, rx data ring will be disabled\n", sz);
> 
> Here, it seems more appropriate to use "failed to".
> 
> >   			adapter->rxdataring_enabled = false;
> >   		}
> >   	} else {

Agreed.


Kind regards,
-- 
Aaron Tomlin