From: Eric Dumazet <eric.dumazet@gmail.com>
To: Joe Perches <joe@perches.com>
Cc: Tom Herbert <therbert@google.com>,
David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>
Subject: Re: [RFC PATCH] dynamic_queue_limit.h: Make the struct ___cacheline_aligned_on_smp
Date: Fri, 07 Dec 2012 08:54:29 -0800 [thread overview]
Message-ID: <1354899269.26405.12.camel@edumazet-glaptop> (raw)
In-Reply-To: <1354897761.29937.45.camel@joe-AO722>
On Fri, 2012-12-07 at 08:29 -0800, Joe Perches wrote:
> Well Maybe Tom can provide some information as to why
> the limit variable was cacheline_aligned_in_smp and not
> the struct.
>
> I didn't find any discussion about it.
>
The struct _is_ cache line aligned, since it contains one field needing
cache line alignment. Its pretty clear to us.
There are two cache lines in it.
We don't one a single cache line, but two, for performance reasons.
If you believe its wrong, you have to provide the performance study, not
me, as I don't have time to spend cycles on this. We did this a long
time ago.
If you want to save few bytes on your kernel, redefine
__cacheline_aligned_on_smp to empty, and you'll be ok.
prev parent reply other threads:[~2012-12-07 16:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-07 14:58 [RFC PATCH] dynamic_queue_limit.h: Make the struct ___cacheline_aligned_on_smp Joe Perches
2012-12-07 15:55 ` Eric Dumazet
2012-12-07 16:05 ` Joe Perches
2012-12-07 16:19 ` Eric Dumazet
2012-12-07 16:29 ` Joe Perches
2012-12-07 16:42 ` Ben Hutchings
2012-12-07 16:54 ` Eric Dumazet [this message]
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