netdev - [PATCH] net: make struct net_device::min_header

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Message-ID: <20170410082526.GC24514@avx2>
Date:   Mon, 10 Apr 2017 11:25:26 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org
Subject: [PATCH] net: make struct net_device::min_header_len 8-bit

This field is never big enough to warrant 16-bitness.

8-bit accesses enjoy shorted encoding on i386/x86_64 than 16-bit
accesses:

	add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-10 (-10)
	function                                     old     new   delta
	loopback_setup                               169     164      -5
	ether_setup                                  148     143      -5

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 include/linux/netdevice.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1715,7 +1715,7 @@ struct net_device {
 	unsigned int		max_mtu;
 	unsigned short		type;
 	unsigned short		hard_header_len;
-	unsigned short		min_header_len;
+	unsigned char		min_header_len;
 
 	unsigned short		needed_headroom;
 	unsigned short		needed_tailroom;