Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752445AbbBWVOB (ORCPT ); Mon, 23 Feb 2015 16:14:01 -0500 Received: from mout.gmx.net ([212.227.17.21]:59107 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752076AbbBWVOA (ORCPT ); Mon, 23 Feb 2015 16:14:00 -0500 Message-ID: <54EB9781.504@gmx.de> Date: Mon, 23 Feb 2015 22:11:29 +0100 From: Heinrich Schuchardt User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: Oleg Nesterov CC: Andrew Morton , Aaron Tomlin , Andy Lutomirski , Davidlohr Bueso , David Rientjes , "David S. Miller" , Fabian Frederick , Guenter Roeck , "H. Peter Anvin" , Ingo Molnar , Jens Axboe , Joe Perches , Johannes Weiner , Kees Cook , Michael Marineau , "Paul E. McKenney" , Peter Zijlstra , Prarit Bhargava , Rik van Riel , Rusty Russell , Steven Rostedt , Thomas Gleixner , Vladimir Davydov , linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4 v4] kernel/fork.c: memory hotplug updates max_threads References: <20150222075825.GA20626@gmail.com> <1424722477-23758-1-git-send-email-xypron.glpk@gmx.de> <1424722477-23758-5-git-send-email-xypron.glpk@gmx.de> <20150223205052.GA26955@redhat.com> <20150223205412.GB26955@redhat.com> In-Reply-To: <20150223205412.GB26955@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K0:0KK3pDQPoLHHoYIP0ARM2WU0XMeMeisemAf8747UnAt3DsJUeli O4iXyZ2e3ptxD4tIP6XXDhti3pKcEkX0mqeK8vaZ3YDevacU66TPLoPRt4y4GuXlVkBWhGm kRYcH2cXjXHEeJ5BMGTDIsilFDzAOitUh9hC09FDYZizZBAj323A+470i1W3pxdBNZwjlUV HDdfAPQto0WIRck9YZsqw== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1922 Lines: 61 On 23.02.2015 21:54, Oleg Nesterov wrote: > On 02/23, Oleg Nesterov wrote: >> >> On 02/23, Heinrich Schuchardt wrote: >>> >>> +static int memory_hotplug_callback(struct notifier_block *self, >>> + unsigned long action, void *arg) >>> +{ >>> + switch (action) { >>> + case MEM_ONLINE: >>> + /* >>> + * If memory was added, try to maximize the number of allowed >>> + * threads. >>> + */ >>> + set_max_threads(UINT_MAX); >>> + break; >>> + case MEM_OFFLINE: >>> + /* >>> + * If memory was removed, try to keep current value. >>> + */ >>> + set_max_threads(max_threads); >>> + break; >>> + } >> >> can't understand... set_max_threads() added by 1/4 ignore its argument. >> Why does it need "int max_threads_suggested" then? > > OOPS sorry, missed 2/4 ;) > >> And it changes the swapper/0's rlimits. This is pointless after we fork >> /sbin/init. So should writing to /proc/sys/max_threads update the limits of all processes? >> >> It seems to me these patches need some cleanups. Plus I am not sure the >> kernel should update max_threads automatically, we have the "threads-max" >> sysctl. The idea in the original version of fork_init is that max_threads should be chosen such that the memory needed to store the meta-information of max_threads threads should only be 1/8th of the total memory. Somebody adding or removing memory will not necessarily update /proc/sys/kernel/threads-max. This means that if I remove 90 % of the memory I get to a situation where max_threads allows so many threads to be created that the meta-information occupies all memory. With patch 4/4 max_threads is automatically reduced in this case. Best regards Heinrich -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/