netdev - Re: [PATCH net-next v2] net: remove gfp_mask from napi_alloc

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Date: Thu, 28 Mar 2024 12:48:33 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Simon Horman <horms@...nel.org>
Cc: Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net, netdev@...r.kernel.org, 
	pabeni@...hat.com, Alexander Lobakin <aleksander.lobakin@...el.com>, alexs@...nel.org, 
	siyanteng@...ngson.cn, jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com, 
	alexandre.torgue@...s.st.com, joabreu@...opsys.com, mcoquelin.stm32@...il.com, 
	intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH net-next v2] net: remove gfp_mask from napi_alloc_skb()

On Thu, Mar 28, 2024 at 12:32 PM Simon Horman <horms@...nel.org> wrote:
>
> On Tue, Mar 26, 2024 at 09:02:12PM -0700, Jakub Kicinski wrote:
> > __napi_alloc_skb() is napi_alloc_skb() with the added flexibility
> > of choosing gfp_mask. This is a NAPI function, so GFP_ATOMIC is
> > implied. The only practical choice the caller has is whether to
> > set __GFP_NOWARN. But that's a false choice, too, allocation failures
> > in atomic context will happen, and printing warnings in logs,
> > effectively for a packet drop, is both too much and very likely
> > non-actionable.
> >
> > This leads me to a conclusion that most uses of napi_alloc_skb()
> > are simply misguided, and should use __GFP_NOWARN in the first
> > place. We also have a "standard" way of reporting allocation
> > failures via the queue stat API (qstats::rx-alloc-fail).
> >
> > The direct motivation for this patch is that one of the drivers
> > used at Meta calls napi_alloc_skb() (so prior to this patch without
> > __GFP_NOWARN), and the resulting OOM warning is the top networking
> > warning in our fleet.
> >
> > Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> > Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>
> Reviewed-by: Simon Horman <horms@...nel.org>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>