From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751963AbeFDGy3 (ORCPT ); Mon, 4 Jun 2018 02:54:29 -0400 Received: from mx2.suse.de ([195.135.220.15]:54022 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751047AbeFDGy2 (ORCPT ); Mon, 4 Jun 2018 02:54:28 -0400 Date: Mon, 4 Jun 2018 08:54:25 +0200 From: Michal Hocko To: "Eric W. Biederman" Cc: Kirill Tkhai , akpm@linux-foundation.org, peterz@infradead.org, oleg@redhat.com, viro@zeniv.linux.org.uk, mingo@kernel.org, paulmck@linux.vnet.ibm.com, keescook@chromium.org, riel@redhat.com, tglx@linutronix.de, kirill.shutemov@linux.intel.com, marcos.souza.org@gmail.com, hoeun.ryu@gmail.com, pasha.tatashin@oracle.com, gs051095@gmail.com, dhowells@redhat.com, rppt@linux.vnet.ibm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/4] exit: Make unlikely case in mm_update_next_owner() more scalable Message-ID: <20180604065425.GF19202@dhcp22.suse.cz> References: <152473763015.29458.1131542311542381803.stgit@localhost.localdomain> <20180426130700.GP17484@dhcp22.suse.cz> <877enj9uwf.fsf@xmission.com> <20180601135725.GE15278@dhcp22.suse.cz> <87a7sey3ud.fsf@xmission.com> <20180601150219.GG15278@dhcp22.suse.cz> <87y3fyv88o.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87y3fyv88o.fsf@xmission.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 01-06-18 10:25:59, Eric W. Biederman wrote: > Michal Hocko writes: > > > On Fri 01-06-18 09:32:42, Eric W. Biederman wrote: > >> Michal Hocko writes: > > [...] > >> > Group leader exiting early without tearing down the whole thread > >> > group should be quite rare as well. No question that somebody might do > >> > that on purpose though... > >> > >> The group leader exiting early is a completely legitimate and reasonable > >> thing to do, even if it is rare. > > > > I am not saying it isn't legitimate. But the most common case is the > > main thread waiting for its threads or calling exit which would tear the > > whole group down. Is there any easy way to achieve this other than tkill > > to group leader? Calling exit(3) from the leader performs group exit > > IIRC. > > pthread_exit from the group leader. Right, forgot to mention this one but this would be quite exotic, right? > > I am not arguing this is non-issue. And it certainly is a problem once > > somebody wants to be nasty... I was more interested how often this > > really happens for sane workloads. > > That is a fair question. All I know for certain is that whatever Kirill > Tkhai's workload was it was triggering this the slow path. Yeah, that was exactly why I've asked that originally. It must be something pretty special ;) -- Michal Hocko SUSE Labs