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

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Date:	Tue, 28 May 2013 09:29:37 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rafael Aquini <aquini@...hat.com>
Cc:	Ben Greear <greearb@...delatech.com>,
	Francois Romieu <romieu@...zoreil.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,
	riel@...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 Tue, 2013-05-28 at 13:15 -0300, Rafael Aquini wrote:

> The real problem seems to be that more and more the network stack (drivers, perhaps)
> is relying on chunks of contiguous page-blocks without a fallback mechanism to
> order-0 page allocations. When memory gets fragmented, these alloc failures
> start to pop up more often and they scare ordinary sysadmins out of their paints.
> 

Where do you see that ?

I see exactly the opposite trend. 

We have less and less buggy drivers, and we want to catch last
offenders.

> The big point of this change was to attempt to relief some of these warnings 
> which we believed as being useless, since the net stack would recover from it
> by re-transmissions.
> We might have misjudged the scenario, though. Perhaps a better approach would be
> making the warning less verbose for all page-alloc failures. We could, perhaps,
> only print a stack-dump out, if some debug flag is passed along, either as
> reference, or by some CONFIG_DEBUG_ preprocessor directive.


warn_alloc_failed() uses the standard DEFAULT_RATELIMIT_INTERVAL which
is very small (5 * HZ)

I would bump nopage_rs to somethin more reasonable, like one hour or one
day.




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