linux-kernel - Re: [BUG] perf tests: Test converting perf time to TSC

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Message-ID: <20131003135748.GK28601@twins.programming.kicks-ass.net>
Date:	Thu, 3 Oct 2013 15:57:48 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>, mingo@...nel.org,
	tglx@...utronix.de, hpa@...or.com
Subject: Re: [BUG] perf tests: Test converting perf time to TSC

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?
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