From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 18/21] Remove host_alarm_timer hacks. Date: Thu, 30 Apr 2009 08:37:01 -0500 Message-ID: <49F9A97D.7050004@us.ibm.com> References: <1241040038-17183-1-git-send-email-aliguori@us.ibm.com> <1241040038-17183-19-git-send-email-aliguori@us.ibm.com> <49F972EB.3040208@redhat.com> <49F9A56C.5000705@us.ibm.com> <49F9A6BA.5040702@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from e1.ny.us.ibm.com ([32.97.182.141]:36456 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756703AbZD3NhD (ORCPT ); Thu, 30 Apr 2009 09:37:03 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e1.ny.us.ibm.com (8.13.1/8.13.1) with ESMTP id n3UDXVQw015387 for ; Thu, 30 Apr 2009 09:33:31 -0400 Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n3UDb3HE038728 for ; Thu, 30 Apr 2009 09:37:03 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n3UDb29Y011667 for ; Thu, 30 Apr 2009 09:37:03 -0400 In-Reply-To: <49F9A6BA.5040702@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Anthony Liguori wrote: >> In modern KVM, the IO thread is capable of interrupting the CPU >> whenever it needs to process IO. Therefore this "problem" no longer >> exists. >> > > It would still be good to verify that the problem no longer exists. > This is not a cosmetic change; some testing is needed to verify it > doesn't introduce new latencies. > N.B. dynticks is the preferred timer in QEMU on Linux. To even hit this code path, you'd have to use an explicit -clock hpet or -clock rtc. I don't have an hpet on my laptop and -clock rtc boots just as fast as it did before. Do we really care about optimizing latency with -clock rtc though? -- Regards, Anthony Liguori