netdev - Re: [Patch net-next] tcp_metrics: rearrange fields to avoid holes

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Message-ID: <1375241828.22980.6.camel@cr0>
Date:	Wed, 31 Jul 2013 11:37:08 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>
Subject: Re: [Patch net-next] tcp_metrics: rearrange fields to avoid holes

On Tue, 2013-07-30 at 20:24 -0700, Eric Dumazet wrote:
> On Wed, 2013-07-31 at 11:13 +0800, Cong Wang wrote:
> > On Tue, 2013-07-30 at 20:08 -0700, Eric Dumazet wrote:
> > > 
> > > Oh well, this patch is pure noise...
> > > 
> > > 
> > 
> > Mind to be specific?
> > 
> > I know saving 8 bytes is not interesting for you, but it is for me,
> > since I need some room in struct tcp_metrics_block for union inet_addr.
> > With this patch, I don't have to make struct tcp_metrics_block expand to
> > 3 cachelines. :)
> 
> Do you see how this explanation is rather different than the one you
> gave in the changelog ?
> 
> Its 3 lines, instead of all this pahole noise.

So, you mean this patch only makes sense after my union inet_addr? If
so, I will merge it into my inet_addr patch.

> 
> And it would be more logical to put the "unsigned long last_syn_loss" at
> the beginning of the structure, instead after an array of 17 bytes.
> 

Agreed.

Thanks!

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