netdev - Re: [PATCH net-next v2] net: use bigger pages in __netdev_alloc

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Date:	Thu, 27 Sep 2012 19:30:28 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	alexander.h.duyck@...el.com, netdev@...r.kernel.org, bcrl@...ck.org
Subject: Re: [PATCH net-next v2] net: use bigger pages in
 __netdev_alloc_frag

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 26 Sep 2012 18:46:57 +0200

> From: Eric Dumazet <edumazet@...gle.com>
> 
> We currently use percpu order-0 pages in __netdev_alloc_frag
> to deliver fragments used by __netdev_alloc_skb()
> 
> Depending on NIC driver and arch being 32 or 64 bit, it allows a page to
> be split in several fragments (between 1 and 8), assuming PAGE_SIZE=4096
> 
> Switching to bigger pages (32768 bytes for PAGE_SIZE=4096 case) allows :
> 
> - Better filling of space (the ending hole overhead is less an issue)
> 
> - Less calls to page allocator or accesses to page->_count
> 
> - Could allow struct skb_shared_info futures changes without major
>   performance impact.
> 
> This patch implements a transparent fallback to smaller
> pages in case of memory pressure.
> 
> It also uses a standard "struct page_frag" instead of a custom one.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Alexander Duyck <alexander.h.duyck@...el.com>
> Cc: Benjamin LaHaise <bcrl@...ck.org>

Applied.
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