From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Winchell Subject: Re: (progress on hpet accuracy) and Re: [PATCH] Add a timer mode that disables pending missed ticks Date: Wed, 05 Mar 2008 12:42:56 -0500 Message-ID: <47CEDBA0.20103@virtualiron.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: "dan.magenheimer@oracle.com" , "xen-devel@lists.xensource.com" , Deepak Patel , Dave Winchell List-Id: xen-devel@lists.xenproject.org Keir Fraser wrote: >On 5/3/08 17:25, "Dave Winchell" wrote: > > > >>In 2.6.9, it looks like cur_timer->mark_offset() call from >>timer_interrupt in >>32 bit arch/i386/kernel/time.c invokes, for hpet, mark_offset_hpet(), >>which computes >>missed ticks based on hpet counter. mark_offset_pit() does nothing. >>mark_offset_tsc() does compute missed ticks. >> >>In 64 bit 2.6.9, the timer_interrupt() in arch/x86_64/time.c does hpet >>reads directly HPET_T0_CMP, HPET_COUNTER to calculate missed ticks. >> >>So from the code perspective, it looks like missed ticks are computed >>for 32 >>and 64 bit Linux using hpet clocksource. >> >> > >Ah. I looked at 2.6.18 which seems to have neither the mark_offset nor the >GENERIC_TIME approach in its arch/i386 time code. But yeah, it does look >like in general Linux 2.6 is robust to missed ticks when using hpet. That's >good. > >Do you see and simply ignore warning messages from 64-bit Linux when using >hpet (or otherwise not doing missed-tick handling in Xen), by the way? I >know 64-bit Linux is keen to warn about missed ticks, although it does look >like at least the warning is one shot. > > I see the one shot messages on 64 bit and no complaints at all on 4u432 Linux. And I have been ignoring them. > -- Keir > > > >