linux-kernel - Re: [PATCH 10/17] netvm: Allow skb allocation to use PFMEMALLOC reserves

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Message-ID: <20120622112750.GA6596@breakpoint.cc>
Date:	Fri, 22 Jun 2012 13:27:51 +0200
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	Linux-Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>, Neil Brown <neilb@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Christie <michaelc@...wisc.edu>,
	Eric B Munson <emunson@...bm.net>
Subject: Re: [PATCH 10/17] netvm: Allow skb allocation to use PFMEMALLOC
 reserves

On Fri, Jun 22, 2012 at 11:54:51AM +0100, Mel Gorman wrote:
> > This is mostly used by nic to refil their RX skb pool. You add the
> > __GFP_MEMALLOC to the allocation to rise the change of a successfull refill
> > for the swap case.
> > A few drivers use build_skb() to create the skb. __netdev_alloc_skb()
> > shouldn't be affected since the allocation happens with GFP_ATOMIC. Looking at
> > TG3 it uses build_skb() and get_pages() / kmalloc(). Shouldn't this be some
> > considered?
> > 
> 
> While TG3 is not exactly as you describe after rebasing build_skb should
> make a similar check to __alloc_skb. As it is always used for RX allocation
> from the skbuff_head_cache cache the following should be suitable. Thanks.

As Eric pointed out you end up in netdev_alloc_frag() which is using
alloc_page(). This is also used by __netdev_alloc_skb().

Sebastian
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