netdev - Re: [PATCH 2/4 net-next] tg3: provide frags as skb head

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 27 Apr 2012 17:33:06 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
	Tom Herbert <therbert@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Matt Carlson <mcarlson@...adcom.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Michael Chan <mchan@...adcom.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Maciej Żenczykowski <maze@...gle.com>
Subject: Re: [PATCH 2/4 net-next] tg3: provide frags as skb head

On Fri, 2012-04-27 at 12:34 +0200, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> This patch converts tg3 driver, one of our reference drivers, to use new
> build_skb() api in frag mode.
> 
> Instead of using kmalloc() to allocate the memory block that will be
> used by build_skb() as skb->head, we use a page fragment.
> 
> This is a followup of patch "net: allow skb->head to be a page fragment"
> 
> This allows GRO, TCP coalescing, and splice() to be more efficient.
> 
> Incidentally, this also removes SLUB slow path contention in kfree()
[...]
> @@ -5617,17 +5626,48 @@ static void tg3_tx(struct tg3_napi *tnapi)
>  	}
>  }
>  
> +static void *tg3_frag_alloc(struct tg3_rx_prodring_set *tpr)
> +{
> +	void *data;
> +
> +	if (tpr->rx_page_size < TG3_FRAGSIZE) {
> +		struct page *page = alloc_page(GFP_ATOMIC);
> +
> +		if (!page)
> +			return NULL;
> +		atomic_add((PAGE_SIZE / TG3_FRAGSIZE) - 1, &page->_count); 
> +		tpr->rx_page_addr = page_address(page);
[...]

page_address() may return NULL if CONFIG_HIGHMEM is enabled.  And that's
going to be a general problem with this scheme on 32-bit machines.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html