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Date: Thu, 3 Oct 2013 15:57:48 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        linux-kernel@vger.kernel.org, David Ahern <dsahern@gmail.com>,
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        Paul Mackerras <paulus@samba.org>,
        Stephane Eranian <eranian@google.com>, mingo@kernel.org,
        tglx@linutronix.de, hpa@zytor.com
Subject: Re: [BUG] perf tests: Test converting perf time to TSC
Message-ID: <20131003135748.GK28601@twins.programming.kicks-ass.net>
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On Thu, Oct 03, 2013 at 02:49:09PM +0300, Adrian Hunter wrote:
> You can boot with notsc and perf still seems to work
> e.g.
> 
> $ dmesg | grep -i tsc
> [    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-3.11.0+ root=UUID=f1b4c71a-15aa-41a6-8898-cdde49966bce ro ignore_loglevel earlyprintk=ttyS0 console=ttyS0,115200n8 no_console_suspend notsc=1
> [    0.000000] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.11.0+ root=UUID=f1b4c71a-15aa-41a6-8898-cdde49966bce ro ignore_loglevel earlyprintk=ttyS0 console=ttyS0,115200n8 no_console_suspend notsc=1
> [    0.000000] tsc: Kernel compiled with CONFIG_X86_TSC, cannot disable TSC completely
> [    0.000000] tsc: Fast TSC calibration using PIT
> [    0.004000] tsc: Detected 2593.932 MHz processor
> [    0.224000] TSC deadline timer enabled

Yeah, and we still use the TSC deadline timer too.. I think we should
seriously consider removing the notsc option. I really don't know what
its good for.

Thomas, Ingo, hpa?