netdev - Re: [PATCH net] bna: page allocation during interrupts to use a mempool.

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Message-ID: <1412646735.11091.93.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 06 Oct 2014 18:52:15 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Eric Wheeler <netdev@...ts.ewheeler.net>
Cc:	Shahed Shaikh <shahed.shaikh@...gic.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	netdev <netdev@...r.kernel.org>,
	"rmody@...cade.com" <rmody@...cade.com>,
	Rasesh Mody <rasesh.mody@...gic.com>
Subject: Re: [PATCH net] bna: page allocation during interrupts to use a
 mempool.

On Mon, 2014-10-06 at 18:57 -0700, Eric Wheeler wrote:
> This patch fixes an order:2 memory allocation error backtrace by 
> guaranteeing that memory is available during simultaneous high memory 
> pressure and packet rates when using 9k jumbo frames.
> 
> Tests between two systems (one patched, one not) succeeded with ~1TB of 
> data transferred over DRBD.  As expected, the unpatched host gave 
> warn_alloc_failed's, and the patched host worked correctly.  This patch 
> increases kernel memory usage by 32 order-2 allocation when this module is 
> loaded (512k on x86) which should be negligible on hosts that use 10GbE 
> cards.

This is highly suspect to me.

Most likely yet another truesize lie.

At a first glance, bnad_cq_setup_skb_frags() is buggy here :

skb->truesize += totlen;

With this kind of lies, system can OOM very fast.



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