netdev - Re: [PATCH v3] net: Allow no-cache copy from user on transmit

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Message-Id: <20110401.205252.102551587.davem@davemloft.net>
Date:	Fri, 01 Apr 2011 20:52:52 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	therbert@...gle.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v3] net: Allow no-cache copy from user on transmit

From: David Miller <davem@...emloft.net>
Date: Fri, 01 Apr 2011 20:49:22 -0700 (PDT)

> From: Tom Herbert <therbert@...gle.com>
> Date: Wed, 30 Mar 2011 22:04:32 -0700 (PDT)
> 
>> This patch uses __copy_from_user_nocache (from skb_copy_to_page)
>> on transmit to bypass data cache for a performance improvement.
>> This functionality is configurable per device using ethtool.
> ...
>> Signed-off-by: Tom Herbert <therbert@...gle.com>
> 
> It's early in net-next-2.6, so I've applied this now and we can
> add any fixups and tweaks as needed.

Nevermind, you have some work to do in the generic kernel before I
can add this, because nocache copies are not a universally available
feature, for example on sparc64:

In file included from include/linux/tcp.h:210,
                 from include/linux/ipv6.h:221,
                 from include/net/ip_vs.h:26,
                 from kernel/sysctl_binary.c:6:
include/net/sock.h: In function ‘skb_copy_to_page’:
include/net/sock.h:1406: error: implicit declaration of function ‘__copy_from_user_nocache’
make[1]: *** [kernel/sysctl_binary.o] Error 1
make: *** [kernel] Error 2
make: *** Waiting for unfinished jobs....
In file included from include/linux/if_pppox.h:170,
                 from fs/compat_ioctl.c:38:
include/net/sock.h: In function ‘skb_copy_to_page’:
include/net/sock.h:1406: error: implicit declaration of function ‘__copy_from_user_nocache’
In file included from include/linux/highmem.h:7,
                 from include/linux/pagemap.h:10,
                 from include/linux/blkdev.h:12,
                 from fs/compat_ioctl.c:48:
include/linux/uaccess.h: At top level:
include/linux/uaccess.h:49: error: conflicting types for ‘__copy_from_user_nocache’
include/net/sock.h:1406: note: previous implicit declaration of ‘__copy_from_user_nocache’ was here