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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?MNNjnhyvb5QxAiODsjKYXnwQsnyiQkO0AjHsgwzhN7XucWUWf1YcEOhmipEw?= =?us-ascii?Q?A2Gi9Yx6KWbcwDMgUEgKTGGZREmb5xjinIdWkfrGl6BEEqBiAISUeURY6jLV?= =?us-ascii?Q?w6wsJCtrxDstFgO1i+3wuOuMhVsfbSs1nFt/h2RydDasuQzbCUArqHeMohIa?= =?us-ascii?Q?Vpl/2hzmfh/JhD2DMhovBmFhXjvptkR7Lq85Eqt8KKJBWT8xEPz75HDtN8BK?= =?us-ascii?Q?0IV4HGFy9GyWmE0fjWsARZh35Vehs/GoKfH71CWwoq52B/iKbMVR3m7DQovz?= =?us-ascii?Q?FKHJGDBTpaEAgQpiiqe+5aIQHsLUUNDk0bm3D2acWC21R9MSv1b8QnCaGL/6?= =?us-ascii?Q?v+QRdnJBddcn9ibpqfAF/Ho4Zek/1aujWcAtgiRTVqkAgQ8feUnZtkWrgK8H?= =?us-ascii?Q?i6vJp3nlW3Tz1n4/bjA3hUncIMyopGIXoIipeepapHPMer8wpiniN8mjN2RQ?= =?us-ascii?Q?p9YONNDhRi3OJas29p/B0x2ILtRNdd76TeUN2HV9aSqcV88G7tXrUoJTQilu?= =?us-ascii?Q?9V3U/GdKPMGprgY9V/d6yjoRkCXBYEUAOJwyqXrMFH7UAw5Qc3jv7Cg4sN4f?= =?us-ascii?Q?89v3EKzk6pKNNBmDtNn2vI5pwk/P4bKJ6jW+6OI0MZR5lD/QTUtZ7HXifrHa?= =?us-ascii?Q?bVvpiUSgkghJIlt1pdgiMBHZTbvPljCtwaIjjTzf75pEFle1fWRnABp/SB5/?= =?us-ascii?Q?DkKVDnsEARC86H6myLhLDcZLmy1Ot0FDoQRWwnk62S1HLKkcnVc32ebdV+9Z?= =?us-ascii?Q?dvkZT9IYY8yqjkuLcNERZs2yczi3nJFihQQUK9FDBbpoF+2P8/9BqiJ6EJcx?= =?us-ascii?Q?G2KmINZ/odPg2tLCPulEPnYzrhRngxuS4c0RF1Bizl/SgPdkdk0zBZkHKnu0?= =?us-ascii?Q?KY4qczYYYGu51bZ2HAM9Ayi43HJKA/iBgyLzGNGDcDYK3qTWjUHkeFQoqKj2?= =?us-ascii?Q?QofOPf5VESnpxpl0IomJbziPkrE0Ezo9xwcbbIuUW+ehvEvasjfx/T2qGUVA?= =?us-ascii?Q?W3mnlzeR2qdfC2XgqKaXhbVCCDd3GsAol1J30i5b5zXQccJzkKiRCwxoNZVR?= =?us-ascii?Q?KODM7NqKmyFRG4g9PLLlMWg/RbNIHxfTaW8IPh9t2HqWqqA9ulzTXsPIgzWH?= =?us-ascii?Q?sNacy6TC1yXqWQ97pG4RrW2HQsnuRhPyQVDE3sKz65bZjrDFkKZHD/58NRC6?= =?us-ascii?Q?C1ch7r5ZFn2be0O9ju+BeSgUYc61ywtGOeYSU5oTY1G1bB/zTt+WmbM/Mmd1?= =?us-ascii?Q?WZKpdc9CLxd2mhDCXDeWZ99D+Dn3TyoiW2K4oPrejhQLF+nJ0a2GYvvMZGam?= =?us-ascii?Q?z/JJJ7ueF4Bc9NCfORkcE4+Za3L5gNoDdhGy3krAOXBN/WIzlVW27x1JURqg?= =?us-ascii?Q?pl5NlvhVVY3WF/4AfFAAjLCOk/lPrti8MCVG5fmWo7jatKQgdGUMaL5W4ZyG?= =?us-ascii?Q?VaSkiabZtrXXNB72dYBDWNRdyOT0mVLmvnGZUuHU8+9lHob6l1x25WeE55Uw?= =?us-ascii?Q?LORHZPW2dZmNkQdVwTbWgZuk8/ewcBQjQJBE5oltiOH/kreihMkzU9wKkzFs?= =?us-ascii?Q?aMC8zu8QF1lOoE3ChD58SbAzdCCDqViTwgsnTU7T?= X-MS-Exchange-CrossTenant-Network-Message-Id: 6a117bbf-aa67-4055-85ff-08dad0e6e320 X-MS-Exchange-CrossTenant-AuthSource: MN0PR11MB6304.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Nov 2022 02:18:49.9824 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: axNNfUS+WjIO6+9d+H9N38js4CJOCCtdp9gG+fvndLlp4a+gODYarhbUKB7myJjCTh1iOuMmQR7Akkqp0sscnQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR11MB5868 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 23, 2022 at 01:23:48PM -0800, Paul E. McKenney wrote: > On Wed, Nov 23, 2022 at 10:36:04AM +0800, Feng Tang wrote: > > On Tue, Nov 22, 2022 at 02:07:12PM -0800, Paul E. McKenney wrote: > > [...] > > > > > If PM_TIMER was involved, I would expect 'acpi_pm' instead of > > > > > refined-jiffies. Or am I misinterpreting the output and/or code? > > > > > > > > It's about timing. On a typical server platform, the clocksources > > > > init order could be: > > > > refined-jiffies --> hpet --> tsc-early --> acpi_pm --> tsc > > > > > > > > >From your log, TSC('tsc-early') is disabled before 'acpi_pm' get > > > > initialized, so 'acpi_pm' timer (if exist) had no chance to watchdog > > > > the tsc. > > > > > > > > > Either way, would it make sense to add CLOCK_SOURCE_MUST_VERIFY to > > > > > clocksource_hpet.flags? > > > > > > > > Maybe try below patch, which will skip watchdog for 'tsc-early', > > > > while giving 'acpi_pm' timer a chance to watchdog 'tsc'. > > > > > > > > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c > > > > index cafacb2e58cc..9840f0131764 100644 > > > > --- a/arch/x86/kernel/tsc.c > > > > +++ b/arch/x86/kernel/tsc.c > > > > @@ -1131,8 +1131,7 @@ static struct clocksource clocksource_tsc_early = { > > > > .uncertainty_margin = 32 * NSEC_PER_MSEC, > > > > .read = read_tsc, > > > > .mask = CLOCKSOURCE_MASK(64), > > > > - .flags = CLOCK_SOURCE_IS_CONTINUOUS | > > > > - CLOCK_SOURCE_MUST_VERIFY, > > > > + .flags = CLOCK_SOURCE_IS_CONTINUOUS, > > > > .vdso_clock_mode = VDSO_CLOCKMODE_TSC, > > > > .enable = tsc_cs_enable, > > > > .resume = tsc_resume, > > > > > > Your mainline patch b50db7095fe0 ("x86/tsc: Disable clocksource watchdog > > > for TSC on qualified platorms") mitigates the issue so we are good for > > > the immediate future, at least assuming reliable TSC. > > > > > > But it also disables checking against HPET, hence my question about > > > marking clocksource_hpet.flags with CLOCK_SOURCE_MUST_VERIFY at boot time > > > on systems whose CPUs have constant_tsc, nonstop_tsc, and tsc_adjust. > > > > IIUC, this will make TSC to watchdog HPET every 500 ms. We have got > > report that the 500ms watchdog timer had big impact on some parallel > > workload on big servers, that was another factor for us to seek > > stopping the timer. > > Another approach would be to slow it down. Given the tighter bounds > on skew, it could be done every (say) 10 seconds while allowing > 2 milliseconds skew instead of the current 100 microseconds. Yes, this can reduce the OS noise much. One problem is if we make it a general interface, there is some clocksource whose warp time is less than 10 seconds, like ACPI PM_TIMER (3-4 seconds), and I don't know if other ARCHs have similar cases. > > > Is this about the concern of possible TSC frequency calibration > > issue, as the 40 ms per second drift between HPET and TSC? With > > b50db7095fe0 backported, we also have another patch to force TSC > > calibration for those platforms which get the TSC freq directly > > from CPUID or MSR and don't have such info in dmesg: > > "tsc: Refined TSC clocksource calibration: 2693.509 MHz" > > > > https://lore.kernel.org/lkml/20220509144110.9242-1-feng.tang@intel.com/ > > > > We did met tsc calibration issue due to some firmware issue, and > > this can help to catch it. You can try it if you think it's relevant. > > I am giving this a go, thank you! Thanks for spending time testing it! Thanks, Feng