From: David Ahern <dsahern@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org,
roopa@cumulusnetworks.com
Subject: Re: [PATCH net-next] neighbor: Add protocol attribute
Date: Tue, 11 Dec 2018 08:22:04 -0700 [thread overview]
Message-ID: <1acd4550-997f-cca9-3062-8fd91d92beff@gmail.com> (raw)
In-Reply-To: <20181210.215937.1179843388675835344.davem@davemloft.net>
On 12/10/18 10:59 PM, David Miller wrote:
> From: David Ahern <dsahern@gmail.com>
> Date: Mon, 10 Dec 2018 19:47:33 -0700
>
>> On 12/7/18 4:45 PM, David Miller wrote:
>>>
>>> Right, neigh->ha[] should probably be kept 8-byte aligned.
>>>
>>
>> From what I can see ha is only used with memcpy, and neighbour struct is
>> annotated with __randomize_layout. Are you saying that ha should be
>> marked with __aligned(8)?
>
> People who care about performance probably don't build with randomization
> enabled, do they?
>
> Even though it uses memcpy() it will be faster if it is 8 byte aligned
> and we can probably explicitly take advantage of that alignment even
> more if we add the marking as you suggest perhaps.
>
> Given all of this, what is your opinion?
>
Arguably my take is ethernet centric. I do not see how 8-byte alignment
matters when copying 6 bytes. In my response to Eric I showed ha is
still 4-byte aligned and does not straddle cachelines. Those seem the
more relevant to me.
next prev parent reply other threads:[~2018-12-11 15:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-07 21:49 [PATCH net-next] neighbor: Add protocol attribute David Ahern
2018-12-07 22:20 ` Eric Dumazet
2018-12-07 22:24 ` David Ahern
2018-12-07 23:03 ` Eric Dumazet
2018-12-07 23:45 ` David Miller
2018-12-11 2:47 ` David Ahern
2018-12-11 5:59 ` David Miller
2018-12-11 15:22 ` David Ahern [this message]
2018-12-14 22:38 ` David Miller
-- strict thread matches above, loose matches on Subject: below --
2018-12-15 22:09 David Ahern
2018-12-16 20:15 ` David Miller
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