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SubjectRe: [PATCH] net: don't use kvzalloc for DMA memory
On Wed, Apr 18, 2018 at 01:38:43PM -0700, Eric Dumazet wrote:
>
>
> On 04/18/2018 10:55 AM, Michael S. Tsirkin wrote:
>
> > Imagine you want to pass some data to card.
> > Natural thing is to just put it in a variable and start DMA.
> > However DMA API disallows stack access nowdays,
> > so it's natural to put this within struct device.
> >
> > See e.g.
> >
> > commit a725ee3e44e39dab1ec82cc745899a785d2a555e
> > Author: Andy Lutomirski <luto@kernel.org>
> > Date: Mon Jul 18 15:34:49 2016 -0700
> >
> > virtio-net: Remove more stack DMA
> >
>
> Andy just moved the problem to another one, since at that time we already
> had vmalloc() fallback for at least 2 years.
>
> Note that my original patch had :
>
> p = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
> if (!p)
> p = vzalloc(alloc_size);
>
> So really, normal (less than PAGE_SIZE) allocations would have almost-zero-chance to end up to vmalloc(one_page)

Thanks Eric, I'll fix virtio.


--
MST

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