Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756219AbZDZO7e (ORCPT ); Sun, 26 Apr 2009 10:59:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754948AbZDZO7Z (ORCPT ); Sun, 26 Apr 2009 10:59:25 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:39717 "HELO ustc.edu.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1754793AbZDZO7Y convert rfc822-to-8bit (ORCPT ); Sun, 26 Apr 2009 10:59:24 -0400 Message-ID: <440758024.12507@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: ylmao@mail.ustc.edu.cn From: "Mao Yilu" To: Subject: TSC unstable on Intel Pentium M processor 750 Date: Sun, 26 Apr 2009 22:59:13 +0800 Message-ID: <9E8AFFF282BE4091BA53C5D4F911F6F0@xiaomao> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT X-Mailer: Microsoft Office Outlook 11 thread-index: AcnGe4SH2KXZ7QL4QG2xYqctInFiTA== X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1380 Lines: 15 Hi, I masked all the interrupts except keyboard interrupt before the instruction “hlt”, So the CPU ran nothing until I click the keyboard button. And I used “rdtscll” and “do_gettimeofday” to get the halt time. But the result of “do_gettimeofday” was longer than the one of “rdtscll” about 3s per minute. I don’t know why. I timed some math job using the same way in contrary to the “hlt” instruction. The TSC was not correct either. In 3 minutes, the result of “do_gettimeofday” was longer than the one of “rdtscll” about 5s. The processor is Intel Pentium M processor 750. From the software developer’s manual of Intel, the processor clock of Pentium M processors is impacted by Intel SpeedStep technology, while some other processors is not. Maybe this is another feature Pentium M processors own. Pentium M processors support 5 C-states. I am sure the TSC doesn’t stop in C0 and C1 states. But I am not sure about other states. Maybe other states will stop the clock, and “hlt” instruction will make the CPU into deeper state. These are my guess. I wanna the truth. Thank you. Mao Yilu -- 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/