From: Peter Zijlstra <peterz@infradead.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] perf/x86: Clean up cap_user_time* setting
Date: Mon, 7 Oct 2013 19:40:37 +0200 [thread overview]
Message-ID: <20131007174037.GI3081@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <5252EDBE.7030805@zytor.com>
On Mon, Oct 07, 2013 at 10:22:06AM -0700, H. Peter Anvin wrote:
> CONFIG_X86_TSC is a baseline control option; we shouldn't key
> functionality off of it. It's fine to say notsc -> no tracing, but
> making it a compile-time key makes me a bit uphappy. We cut off 386,
> but cutting of 486 at this point makes me nervous.
The thing that annoys me about notsc is that it disables usage even if
its present.
I've no problem with 486 which simply doesn't have TSC and thus
cpu_has_tsc will be false and other stuff will happen -- and I don't
think my proposition would actually change anything there.
What is completely insane is people using notsc on say a haswell chip
and expecting something sane to happen.
So I'm not proposing we remove !cap_has_tsc support; all I'm proposing
is we remove the notsc knob that avoids using the TSC on perfectly good
hardware.
next prev parent reply other threads:[~2013-10-07 17:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-04 17:31 [tip:perf/core] perf/x86: Clean up cap_user_time* setting tip-bot for Peter Zijlstra
2013-10-04 18:31 ` Adrian Hunter
2013-10-04 18:55 ` Peter Zijlstra
2013-10-06 9:10 ` Ingo Molnar
2013-10-07 9:33 ` Peter Zijlstra
2013-10-07 15:59 ` Peter Zijlstra
2013-10-07 17:22 ` H. Peter Anvin
2013-10-07 17:40 ` Peter Zijlstra [this message]
2013-10-07 18:30 ` H. Peter Anvin
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