From: Christoph Lameter <cl@linux.com>
To: Hugh Dickins <hughd@google.com>
Cc: Pekka Enberg <penberg@kernel.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>, Ingo Molnar <mingo@elte.hu>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Matt Mackall <mpm@selenic.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org
Subject: Re: [PATCH 2/4] slub,rcu: don't assume the size of struct rcu_head
Date: Thu, 17 Mar 2011 10:16:01 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1103171006270.12540@router.home> (raw)
In-Reply-To: <AANLkTikk02f6kLiPFqqAGroJErQkHbJFfHzpHy4Y5P8Y@mail.gmail.com>
On Sun, 6 Mar 2011, Hugh Dickins wrote:
> >> That was so for a long time, but I stopped it just over a year ago
> >> with commit a70caa8ba48f21f46d3b4e71b6b8d14080bbd57a, stop ptlock
> >> enlarging struct page.
> >
> > Strange. I just played around with in in January and the page struct size
> > changes when I build kernels with full debugging. I have some
> > cmpxchg_double patches here that depend on certain alignment in the page
> > struct. Debugging causes all that stuff to get out of whack so that I had
> > to do some special patches to make sure fields following the spinlock are
> > properly aligned when the sizes change.
>
> That puzzles me, it's not my experience and I don't have an
> explanation: do you have time to investigate?
>
> Uh oh, you're going to tell me you're working on an out-of-tree
> architecture with a million cpus ;) In that case, yes, I'm afraid
> I'll have to update the SPLIT_PTLOCK_CPUS defaulting (for a million -
> 1 even).
No I am not working on any out of tree structure. Just regular dual socket
server boxes with 24 processors (which is a normal business machine
configuration these days).
But then there is also CONFIG_GENERIC_LOCKBREAK. That does not affect
things?
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next prev parent reply other threads:[~2011-03-17 15:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-01 8:03 Lai Jiangshan
2011-03-01 13:00 ` Pekka Enberg
2011-03-01 15:11 ` Christoph Lameter
2011-03-02 2:55 ` Lai Jiangshan
2011-03-02 4:31 ` Hugh Dickins
2011-03-02 12:32 ` Christoph Lameter
2011-03-06 19:39 ` Hugh Dickins
2011-03-08 2:17 ` Lai Jiangshan
2011-03-17 15:16 ` Christoph Lameter [this message]
2011-03-19 3:58 ` Hugh Dickins
2011-03-08 18:25 ` Christoph Lameter
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