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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Peter Zijlstra <peterz@infradead.org>
Subject: Re: KVM bug, git bisected
Cc: kosaki.motohiro@jp.fujitsu.com, Rik van Riel <riel@redhat.com>,
       Kent Overstreet <kent.overstreet@gmail.com>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>
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> On Mon, 2010-03-29 at 18:29 +0200, Peter Zijlstra wrote:
> 
> > > Peter, would it be safe to increase PREEMPT_BITS to eg. 10?
> 
> One reason this all sucks massive is that nesting that many spinlocks
> creates a terribly large !preempt section.
> 
> There is nothing that stops someone from creating 64k vmas (or more when
> someone raises that sysctl) and try this, that's just utter suckage.

offtopic: We are plan to increase default maximum vmas limit from 64k
at 1 or 2 years later on 64bit. It was necessary because gdb couldn't
parse >64k vmas (i.e. mainly it's for core dump). but it was solved already.