Message-ID: <438CE416.3060707@t-online.de>
Date: Wed, 30 Nov 2005 00:28:22 +0100
From: Bernd Schmidt <bernds_cb1@t-online.de>
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To: Andi Kleen <ak@suse.de>
CC: Nicholas Miell <nmiell@comcast.net>, Stephane Eranian <eranian@hpl.hp.com>,
       Ray Bryant <raybry@mpdtxmail.amd.com>, discuss@x86-64.org,
       linux-kernel@vger.kernel.org, perfctr-devel@lists.sourceforge.net
Subject: Re: [Perfctr-devel] Re: Enabling RDPMC in user space by default
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Andi Kleen wrote:

> To give an bad analogy RDTSC usage in the last years is
> like explicit spinning wait loops for delays in the earlier
> times. They tended to work on some subset of computers,
> but were always bad and caused problems and people eventually learned
> it was better to use operating system services for this.
> 
> The kernel will probably not disable RDTSC outright,
> but will make it clear in documentation that it's a bad
> idea to use directly and laugh at everybody who runs
> into problems with it.

I happen to have an old program which uses RDTSC frequently for timing 
purposes.  That seemed like a good idea at the time, but I guess it 
should be updated.  The question is, what replacement is there?  I don't 
want to have to use a syscall every 50 instructions or so.  Feel free to 
laugh, but suggesting a workable replacement might be more helpful.


Bernd
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