Date: Fri, 8 Jan 2010 09:52:58 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Christoph Lameter <cl@linux-foundation.org>
cc: Peter Zijlstra <peterz@infradead.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Minchan Kim <minchan.kim@gmail.com>,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "linux-mm@kvack.org" <linux-mm@kvack.org>,
       "hugh.dickins" <hugh.dickins@tiscali.co.uk>,
       Nick Piggin <nickpiggin@yahoo.com.au>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()
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On Fri, 8 Jan 2010, Christoph Lameter wrote:
> 
> Can we at least consider a typical standard business server, dual quad
> core hyperthreaded with 16 "cpus"? Cacheline contention will increase
> significantly there.

I bet it won't be a problem. It's when things go cross-socket that they 
suck. So 16 cpu's across two sockets I wouldn't worry about.

> > Because let's face it - if your workload does several million page faults
> > per second, you're just doing something fundamentally _wrong_.
> 
> You may just want to get your app running and its trying to initialize
> its memory in parallel on all threads. Nothing wrong with that.

Umm. That's going to be limited by the memset/memcpy, not the rwlock, I 
bet.

The benchmark in question literally did a single byte write to each page 
in order to show just the kernel component. That really isn't realistic 
for any real load.

			Linus
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