Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756373AbdCGUm6 (ORCPT ); Tue, 7 Mar 2017 15:42:58 -0500 Received: from mail-cys01nam02on0099.outbound.protection.outlook.com ([104.47.37.99]:25346 "EHLO NAM02-CY1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756291AbdCGUmS (ORCPT ); Tue, 7 Mar 2017 15:42:18 -0500 Authentication-Results: hpe.com; dkim=none (message not signed) header.d=none;hpe.com; dmarc=none action=none header.from=hpe.com; Subject: Re: [PATCH 1/2] x86/platform: Add a low priority low frequency NMI call chain To: Don Zickus , Ingo Molnar References: <20170306181737.059578494@asylum.americas.sgi.com> <20170306181737.322206440@asylum.americas.sgi.com> <20170307074210.GA24782@gmail.com> <20170307152206.4nqqrekwmfqbdn7b@redhat.com> CC: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Dimitri Sivanich , Frank Ramsay , Russ Anderson , Tony Ernst , , From: Mike Travis Message-ID: Date: Tue, 7 Mar 2017 08:00:33 -0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20170307152206.4nqqrekwmfqbdn7b@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [73.222.225.80] X-ClientProxiedBy: BN6PR13CA0002.namprd13.prod.outlook.com (10.175.123.12) To AT5PR84MB0228.NAMPRD84.PROD.OUTLOOK.COM (10.162.138.153) X-MS-Office365-Filtering-Correlation-Id: 32c14d94-c2a1-4d9e-711c-08d465731c65 X-MS-Office365-Filtering-HT: Tenant X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(22001)(48565401081);SRVR:AT5PR84MB0228; X-Microsoft-Exchange-Diagnostics: 1;AT5PR84MB0228;3:Vjnh7gohodiX32u558nzidzrZ12FGxLwgH6Y5QHfpzlUNWizuvvNOm8ZrxEssoq8KnwhNeZiR7IpGYVhab9UqzP+N0Qml2r6Pmr9qXe9PSyXhPNu9gl51B4OdwnYfFutOba9LC4IHqzKdM1VJMaz9AYRB1jZanwoUnhu3X/cxN0Rr4b9wj+JpiVoYwrdF7LEQmQrhJAHszkYlXIsFtAfEvK0l4lt+hB9/bImqY7D5rf9sd4fyv982XsdFbJhD+Lrd2IfGtoXG2qyftD1SGBzHYG9X0+iMCj1qqL0nrKh9CQ=;25:4aXw/YKAbTNLHxlf5y30u9Ylwhb9nk44m11BM9QxZ8/qOgSbseK9R/q/Ysbtgf651BFNWIuasUq1i1epy1qHdWcnMH++GB7gw8iSy0bfS3D4YMt5Is1/NwlHl8TBmH9eHA9mxykYuztWm0R7tucvAVB/RtniGEE6E1S0NqPNZku+NJxKnYtLE/Okk8+qPut7DoAV1Kagm9TDZJYtCDm5lReo2jJcbb6K5QB5wBhkpf6ZyioT00wFKLZ6DECVn+Wwz6MLr5BBYzP4ox1kPO3vm+WAH/Syyhaq0d7RmsObDHLhzBuLeyIjAxx6gNr1p6AWJQYeuZ5FaLfGcMY+udw+8swOHps2lH2GYCewDWKGTZnQTpXCkj7/cO5pr1YxYiuZ70wO9zzBCelbOcARyP6q5+1VfvjRAcTqut1DSiQUHtAxYMvN6PnaHQsfOG6E3kvJ97q4wWlM9XyKLjB99ZOfdg== X-Microsoft-Exchange-Diagnostics: 1;AT5PR84MB0228;31:kgdlFlUkw/gxpOUiIj9gm2cfXI51asQjgB6uPGrr4K411u7Ybv6V8WdjAUBs+FrsZG4u2yC/t92TLWEsn//lY99FN6BmgwMLfkaffBcG4DTEQ022UagHLfWce27v9aK4GaMJAoRr3cfOGfPVvBfZY/M8XP69XITMTM6Adu6w1hJQzj6dXUcXCwFhaiH6a5SqbJrIxluhMcuBjkoCusaqw+BZGI3J+6IJxU436JPN2SM=;20:0R/oaFpLZaQoglxuD+1exFdoa+Oyy6da6+CIRR8AZ5NpY4itCjiCORekLPME1o6f4wWSoQYRl98IsbdxzNAtLn3AqBkvDg38llVFILjneUgGnOLliGB23f2kJsiyDdzeIJmunqinM8UYUnuVHEBqOw8A/TwD0SpMgl7iDglVVbpGmDTQWq5p+8deU9kLVThnfH/3JQtY6a1qGIUBtcg67bhpm5S1fuHA9KPoWj6cAZMtAx6EEnuMrNPYXLWGBTtaLzqvmEJZ47k2H7+CZADcQ2e7q/3eVvLdsVkKDRJDOmYZnne8zrzcpHoNdGQ3FdH8G0i1B0OyU07r5zdtd//v5+4Z1JeEjr4FKO+DVY7B0RPE+4QtP2LTmH6X2pey2O7W4RFRIStqlhEHu2ogwNLhoSSbFEA+5ljbPOJL8ieM4apeSvOiqALsLDX+lrwNM6tciB1UdZpWxgtS9RfL1GaMlrbnCamraS+eSrZfpIuLCyJXbFk8OjLQFDDCAzzpfVvb X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:(227479698468861); 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This mimics the current >>> NMI_UNKNOWN call chain except it eliminates the WARNING message about >>> multiple NMI handlers registering on this call chain. >>> >>> This call chain dramatically lowers the NMI call frequency when high >>> frequency NMI tools are in use, notably the perf tools. It is required >>> for NMI handlers that cannot sustain a high NMI call rate without >>> ramifications to the system operability. >> >> So how about we just turn off that warning instead? I don't remember the last time >> it actually _helped_ us find any kernel or hardware bug - and it has caused tons >> of problems... > > Yeah, that is one way to solve it. :-) Actually just removing the WARNING indication and making it an INFO message would be enough to quiet objections. Is that enough, or should the message be completely removed for UNKNOWN NMI handlers, and left in place for IO_CHECK and SERR NMI handlers? > > Originally I put that in there because the unknown nmi handlers sometime do > not return, making it impossible for the second handler to run. The only two external unknown NMI handlers that I know of is the UV one and the KGDB one. The KGDB one appears to be only claimed if it is exiting an NMI_LOCAL event. And the UV one is only claimed if it as caused by a UV System NMI event. So truly unknown NMI events eventually get to the internal unknown nmi handler. > But you are right, it probably hasn't really helped find any problems. I > wasn't aware of problems it was causing (not that I was looking through > emails to find them either). > > Cheers, > Don > >> >> It's not like we warn about excess regular IRQs either - we either handle them or >> at most increase a counter somewhere. We could do the same for NMIs: introduce a >> counter somewhere that counts the number of seemingly unhandled NMIs. >> >> But in any case, we should not spam the kernel log, neither with high, nor with >> low frequency. >> >> Thanks, >> >> Ingo