netdev - Re: [Patch v2] skbuff: Hide GFP_ATOMIC page allocation failures for dropped packets

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Message-ID: <1369721054.3301.531.camel@edumazet-glaptop>
Date:	Mon, 27 May 2013 23:04:14 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Rik van Riel <riel@...hat.com>, atomlin@...hat.com,
	netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	pshelar@...ira.com, mst@...hat.com, alexander.h.duyck@...el.com,
	aquini@...hat.com, sergei.shtylyov@...entembedded.com,
	linux-kernel@...r.kernel.org
Subject: Re: [Patch v2] skbuff: Hide GFP_ATOMIC page allocation failures for
 dropped packets

On Mon, 2013-05-27 at 21:31 -0700, Joe Perches wrote:

> I think the __alloc_skb alloc failure message is ok,
> but maybe there shouldn't be something "scary" like
> a dump_stack.
> 
> Maybe this site should use a trivial debug error
> message like below instead.
> ---

Oh well.

If dump_stack are scary, they are scary for every k[mz]alloc() users,
not only __alloc_skb_alloc()

I just said : Please do not add GFP_NOWARN to thousand of call sites,
and you suggest adding more code in network fast path. (???)

This is not a trivial code, we are speaking of a very sensitive one.

Let mm guys explain in what cases a full stack trace is nice to have,
and in what cases its useless. An heuristic should be defined in mm tree
for that, and not spread everywhere.

There must be a reason GFP_NOWARN is seldom used in the kernel, even if
most callers are able to recover properly from a failed memory
allocation.

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