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

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Message-ID: <20240328113202.GH403975@kernel.org>
Date: Thu, 28 Mar 2024 11:32:02 +0000
From: Simon Horman <horms@...nel.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
	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 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>