From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: Enhance perf to support KVM
Date: Tue, 02 Mar 2010 17:46:03 +0100
Message-ID: <4B8D40CB.1090905@redhat.com>
References: <20100226090147.GH15885@elte.hu> <4B879A2F.50203@redhat.com> <20100226103545.GA7463@elte.hu> <4B87A6BF.3090301@redhat.com> <20100226111734.GE7463@elte.hu> <4B87B407.2070309@redhat.com> <20100226124646.GB19476@elte.hu> <4B87C494.4090306@redhat.com> <20100226131614.GB2518@elte.hu> <4B87D4FB.2060200@redhat.com> <20100226142318.GE23422@elte.hu>
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Cc: Avi Kivity <avi@redhat.com>,
	"Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>, ming.m.lin@intel.com,
	sheng.yang@intel.com, Jes Sorensen <Jes.Sorensen@redhat.com>,
	KVM General <kvm@vger.kernel.org>,
	Zachary Amsden <zamsden@redhat.com>,
	Gleb Natapov <gleb@redhat.com>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Fr??d??ric Weisbecker <fweisbec@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Arjan van de Ven <arjan@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
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On 02/26/2010 03:23 PM, Ingo Molnar wrote:
> I do think tools/X and tools/libc would make quite a bit of sense - this is
> one of the better design aspects of FreeBSD et al. It's a mistake that it's
> not being done.

I don't see what it would buy to have tools/libc.  You cannot force 
users to update kernel-space and user-space in lockstep (Apple forced 
you to do that sometimes when I used Macs at work, and it was very very 
inconvenient), so it's not like libc would be able to always assume the 
latest system calls.  There is (relatively) a lot of 
backwards-compatibility code in libc; it's ugly code, but you have to 
live with it.

Any case in which you need lockstep upgrades of kernel and libc for 
bisectability is a bug in libc, and I haven't seen it happen enough to 
be a problem.

Paolo

ps: does it make sense to keep such a long list of recipients???