Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751911AbbFCAkG (ORCPT ); Tue, 2 Jun 2015 20:40:06 -0400 Received: from mga03.intel.com ([134.134.136.65]:6426 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751158AbbFCAj5 (ORCPT ); Tue, 2 Jun 2015 20:39:57 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,543,1427785200"; d="scan'208";a="581017058" Date: Tue, 2 Jun 2015 17:39:38 -0700 From: Andi Kleen To: Andy Lutomirski Cc: Thomas Gleixner , Adrian Hunter , LKML , Linus Torvalds , X86 ML , "H. Peter Anvin" , Len Brown Subject: Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() Message-ID: <20150603003938.GQ1187@tassilo.jf.intel.com> References: <1432194944-29087-1-git-send-email-adrian.hunter@intel.com> <20150602194350.GN1187@tassilo.jf.intel.com> <20150602202037.GO1187@tassilo.jf.intel.com> <20150602233820.GP1187@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1318 Lines: 38 On Tue, Jun 02, 2015 at 05:21:27PM -0700, Andy Lutomirski wrote: > On Tue, Jun 2, 2015 at 4:38 PM, Andi Kleen wrote: > > On Tue, Jun 02, 2015 at 11:03:26PM +0200, Thomas Gleixner wrote: > >> > >> > >> On Tue, 2 Jun 2015, Andi Kleen wrote: > >> > >> > > There's the code in tsc_msr.c. It should be relatively > >> > > straightforward to extend it to cover everything that intel_pstate > >> > > supports. > >> > > >> > That's a good idea, but we still need an always working fallback when the > >> > model number is not available. So Adrian's patch is needed in any > >> > case. > >> > >> Nonsense. The slow calibration is already a working fallback. > > > > Please read Adrian's description again. It's not working when the PIT read is > > too slow. That is when the new algorithm is needed. > > > > tglx's suggestion was to use slow calibration as a fallback. You mean the last fallback we have today? That one doesn't work if the PIT read is too slow. And Adrian's patch is fixing that. -Andi -- ak@linux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/