netdev - RE: [net-next 5/8] net/mlx5e: Calc vlan_tag

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]

Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB0277BF0@AcuExch.aculab.com>
Date:   Wed, 1 Feb 2017 11:20:05 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Saeed Mahameed' <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [net-next 5/8] net/mlx5e: Calc vlan_tag_present only once on
 xmit

From: Saeed Mahameed
> Sent: 31 January 2017 20:59
> Cache skb_vlan_tag_present(skb) and pass it wherever needed in xmit
> routines.
...

Does this actually generate better code?
It is quite likely that your 'vlan_present' variable ends up being on stack.
Whereas the 'skb' is likely to be in a register.
In which case the two loads are likely to be must the same and your
change has added a write to the stack.

	David