Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752575AbdHVTzm (ORCPT ); Tue, 22 Aug 2017 15:55:42 -0400 Received: from mga14.intel.com ([192.55.52.115]:48781 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751768AbdHVTzk (ORCPT ); Tue, 22 Aug 2017 15:55:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,413,1498546800"; d="scan'208";a="303233670" From: "Liang, Kan" To: Linus Torvalds CC: Mel Gorman , Mel Gorman , "Kirill A. Shutemov" , Tim Chen , Peter Zijlstra , "Ingo Molnar" , Andi Kleen , Andrew Morton , Johannes Weiner , Jan Kara , linux-mm , Linux Kernel Mailing List Subject: RE: [PATCH 1/2] sched/wait: Break up long wake list walk Thread-Topic: [PATCH 1/2] sched/wait: Break up long wake list walk Thread-Index: AQHTFWNBYSKZKyu5OE6Y+fM96SxNwqKEIDEAgASaOPD//398AIAAsKCA//+X4wCAAQZZgIAAplUA//+BiwAAFSW90P//ia2AgAASl4CAAAVjAIAEq10A//91k2D//XJ4kIAEpo4A//9gzkA= Date: Tue, 22 Aug 2017 19:55:37 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F0775378A377@SHSMSX103.ccr.corp.intel.com> References: <37D7C6CF3E00A74B8858931C1DB2F0775378761B@SHSMSX103.ccr.corp.intel.com> <20170818122339.24grcbzyhnzmr4qw@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F077537879BB@SHSMSX103.ccr.corp.intel.com> <20170818144622.oabozle26hasg5yo@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F07753787AE4@SHSMSX103.ccr.corp.intel.com> <20170818185455.qol3st2nynfa47yc@techsingularity.net> <20170821183234.kzennaaw2zt2rbwz@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F07753788B58@SHSMSX103.ccr.corp.intel.com> <37D7C6CF3E00A74B8858931C1DB2F0775378A24A@SHSMSX103.ccr.corp.intel.com> In-Reply-To: Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiOTM2YTBlMWMtOTBhMC00NTU5LWJhYjktYWM2YTk5N2YwOTJkIiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX0lDIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE2LjUuOS4zIiwiVHJ1c3RlZExhYmVsSGFzaCI6Ino4cVJpRjl2RFVFU2dCRTdqRXBHbHFGek4wc0lXTHpMcjZCZEhLZmx2Qnc9In0= x-ctpclassification: CTP_IC dlp-product: dlpe-windows dlp-version: 10.0.102.7 dlp-reaction: no-action x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id v7MJtlsb016756 Content-Length: 731 Lines: 30 > So I propose testing the attached trivial patch. It doesn’t work. The call stack is the same. 100.00% (ffffffff821af140) | ---wait_on_page_bit __migration_entry_wait migration_entry_wait do_swap_page __handle_mm_fault handle_mm_fault __do_page_fault do_page_fault page_fault | |--40.62%--0x123a2 | start_thread | > It may not do anything at all. > But the existing code is actually doing extra work just to be fragile, in case the > scenario above can happen. > > Comments? > > Linus