All of lore.kernel.org
 help / color / mirror / Atom feed
From: Alexander Duyck <alexander.h.duyck@intel.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: "Kirsher, Jeffrey T" <jeffrey.t.kirsher@intel.com>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"gospo@redhat.com" <gospo@redhat.com>,
	"bphilips@novell.com" <bphilips@novell.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	"x86@kernel.org" <x86@kernel.org>
Subject: Re: [net-next-2.6 PATCH v2] x86: Align skb w/ start of cacheline on newer core 2/Xeon Arch
Date: Thu, 01 Jul 2010 13:37:27 -0700	[thread overview]
Message-ID: <4C2CFC87.6020003@intel.com> (raw)
In-Reply-To: <87tyojzbjm.fsf@basil.nowhere.org>

Andi Kleen wrote:
> Jeff Kirsher <jeffrey.t.kirsher@intel.com> writes:
> 
> 
> Sorry for the late comment.
> 
>>  
>> +#ifdef CONFIG_MCORE2
>> +/*
>> + * We handle most unaligned accesses in hardware.  On the other hand
>> + * unaligned DMA can be quite expensive on some Nehalem processors.
>> + *
>> + * Based on this we disable the IP header alignment in network drivers.
>> + */
>> +#define NET_IP_ALIGN	0
>> +#endif
>>  #endif /* _ASM_X86_SYSTEM_H */
> 
> The ifdef should be imho dropped and the option be made unconditional
> for all x86. I am not aware of any x86 core where unalignment is really
> slow. This would increase the chance of it actually working on many
> configurations which do not necessarily optimize for Core2.
> 
> -Andi

Seems to make sense to me.  I will see about generating a patch that 
drops the check for CONFIG_MCORE2.

Thanks,

Alex

  reply	other threads:[~2010-07-01 20:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-06-30  4:38 [net-next-2.6 PATCH v2] x86: Align skb w/ start of cacheline on newer core 2/Xeon Arch Jeff Kirsher
2010-06-30 21:28 ` David Miller
2010-06-30 21:32   ` H. Peter Anvin
2010-06-30 21:34     ` David Miller
2010-07-01 11:28 ` Andi Kleen
2010-07-01 20:37   ` Alexander Duyck [this message]
2010-07-01 20:41     ` H. Peter Anvin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4C2CFC87.6020003@intel.com \
    --to=alexander.h.duyck@intel.com \
    --cc=andi@firstfloor.org \
    --cc=bphilips@novell.com \
    --cc=davem@davemloft.net \
    --cc=gospo@redhat.com \
    --cc=hpa@zytor.com \
    --cc=jeffrey.t.kirsher@intel.com \
    --cc=mingo@redhat.com \
    --cc=netdev@vger.kernel.org \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.