From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 14B6C6B02B4 for ; Wed, 14 Jun 2017 20:28:20 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id d191so14565805pga.15 for ; Wed, 14 Jun 2017 17:28:20 -0700 (PDT) Received: from mail-pf0-x229.google.com (mail-pf0-x229.google.com. [2607:f8b0:400e:c00::229]) by mx.google.com with ESMTPS id 1si1030047pgu.95.2017.06.14.17.28.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Jun 2017 17:28:19 -0700 (PDT) Received: by mail-pf0-x229.google.com with SMTP id s66so8016278pfs.1 for ; Wed, 14 Jun 2017 17:28:19 -0700 (PDT) Date: Wed, 14 Jun 2017 17:28:16 -0700 (PDT) From: David Rientjes Subject: Re: Sleeping BUG in khugepaged for i586 In-Reply-To: <20170612062918.GA4145@dhcp22.suse.cz> Message-ID: References: <1e883924-9766-4d2a-936c-7a49b337f9e2@lwfinger.net> <9ab81c3c-e064-66d2-6e82-fc9bac125f56@suse.cz> <20170608144831.GA19903@dhcp22.suse.cz> <20170608170557.GA8118@bombadil.infradead.org> <20170608201822.GA5535@dhcp22.suse.cz> <20170608203046.GB5535@dhcp22.suse.cz> <20170610080941.GA12347@dhcp22.suse.cz> <20170612062918.GA4145@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Matthew Wilcox , Vlastimil Babka , Larry Finger , Andrew Morton , LKML , linux-mm@kvack.org On Mon, 12 Jun 2017, Michal Hocko wrote: > > These are not soft lockups, these are need_resched warnings. We monitor > > how long need_resched has been set and when a thread takes an excessive > > amount of time to reschedule after it has been set. A loop of 512 pages > > with ptl contention and doing {clear,copy}_user_highpage() shows that > > need_resched can sit without scheduling for an excessive amount of time. > > How much is excessive here? We monitor anything that holds the cpu for more than 1/20th of a second, but this specific occurrence has been observed for ~1/8th. The majority of mm/ is quite good in this regard. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org