netdev - Re: [PATCH net-next] net: macb: replace literal constant with NET_IP

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, 03 Jul 2015 18:39:13 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Joe Perches <joe@...ches.com>,
	Nicolae Rosia <nicolae.rosia@...tsign.ro>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	'Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: [PATCH net-next] net: macb: replace literal constant with
 NET_IP_ALIGN

On Fri, 2015-07-03 at 16:18 +0000, David Laight wrote:

> Even on x86 aligning the ethernet receive data on a 4n+2
> boundary is likely to give marginally better performance
> than aligning on a 4n boundary.

You are coming late to the party.

Intel guys decided to change NET_IP_ALIGN to 0 (it was 2 in the past)

commit ea812ca1b06113597adcd8e70c0f84a413d97544
Author: Alexander Duyck <alexander.h.duyck@...el.com>
Date:   Tue Jun 29 18:38:00 2010 +0000

    x86: Align skb w/ start of cacheline on newer core 2/Xeon Arch
    
    x86 architectures can handle unaligned accesses in hardware, and it has
    been shown that unaligned DMA accesses can be expensive on Nehalem
    architectures.  As such we should overwrite NET_IP_ALIGN to resolve
    this issue.
    
    Cc: Thomas Gleixner <tglx@...utronix.de>
    Cc: Ingo Molnar <mingo@...hat.com>
    Cc: "H. Peter Anvin" <hpa@...or.com>
    Cc: x86@...nel.org
    Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
    Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
    Acked-by: H. Peter Anvin <hpa@...or.com>
    Signed-off-by: David S. Miller <davem@...emloft.net>


--
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