From: Joerg Roedel <joro@8bytes.org>
To: Vojtech Pavlik <vojtech@suse.cz>
Cc: Andi Kleen <andi@firstfloor.org>,
Joerg Roedel <joerg.roedel@amd.com>,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
linux-kernel@vger.kernel.org, benjamin.serebrin@amd.com
Subject: Re: Whats the purpose of get_cycles_sync()
Date: Wed, 31 Oct 2007 11:23:46 +0100 [thread overview]
Message-ID: <20071031102346.GE29700@8bytes.org> (raw)
In-Reply-To: <20071030220209.GA21142@suse.cz>
Hi Vojtech,
On Tue, Oct 30, 2007 at 11:02:09PM +0100, Vojtech Pavlik wrote:
> The K8's still guarantee that subsequent RDTSCs return increasing
> values, even if the processor reorders them.
>
> What could have been happening then was that the RDTSC instruction might
> have been reordered by the CPU out of the seqlock, causing trouble in
> the calculation.
>
> Anyway, adding the CPUID didn't solve all the problems we've seen back
> then, and so far none of the approaches for using TSC without acquiring
> a spinlock on multi-socket AMD boxes worked 100% correctly.
Can you tell me more about the problems you have seen or give me a
pointer to a mail discussion regarding that problems? Can you also
provide your test program to me please? I want to understand these
problems a bit better.
Joerg
next prev parent reply other threads:[~2007-10-31 10:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-30 17:44 Whats the purpose of get_cycles_sync() Joerg Roedel
2007-10-30 20:21 ` Andi Kleen
2007-10-30 22:02 ` Vojtech Pavlik
2007-10-30 22:42 ` Andi Kleen
2007-10-31 10:23 ` Joerg Roedel [this message]
2007-10-31 10:18 ` Joerg Roedel
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