netdev - Re: [PATCH net-next] net: use bigger pages in __netdev_alloc

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Message-ID: <20120926131110.GL10611@kvack.org>
Date:	Wed, 26 Sep 2012 09:11:10 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.h.duyck@...el.com>
Subject: Re: [PATCH net-next] net: use bigger pages in __netdev_alloc_frag

Hello Eric,

On Wed, Sep 26, 2012 at 11:06:42AM +0200, Eric Dumazet wrote:
> +	int order;
...
> +		for (order = NETDEV_FRAG_PAGE_MAX_ORDER; ;) {
> +			gfp_t gfp = gfp_mask;
> +
> +			if (order)
> +				gfp |= __GFP_COMP | __GFP_NOWARN;
> +			nc->frag.page = alloc_pages(gfp, order);
> +			if (likely(nc->frag.page))
> +				break;
> +			if (--order <= 0)
> +				goto end;
> +		}

I think you probably intended the last if to be "if (--order < 0)", as 
otherwise the alloc will never be attempted with an order 0 page, which 
could harm systems suffering from extreme memory fragmentation.  Cheers,

		-ben
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