From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 18F356B0069 for ; Fri, 21 Oct 2016 02:39:31 -0400 (EDT) Received: by mail-lf0-f69.google.com with SMTP id m193so20510108lfm.7 for ; Thu, 20 Oct 2016 23:39:31 -0700 (PDT) Received: from mail-lf0-f65.google.com (mail-lf0-f65.google.com. [209.85.215.65]) by mx.google.com with ESMTPS id v64si533396lfi.365.2016.10.20.23.39.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2016 23:39:29 -0700 (PDT) Received: by mail-lf0-f65.google.com with SMTP id x79so3932747lff.2 for ; Thu, 20 Oct 2016 23:39:29 -0700 (PDT) Date: Fri, 21 Oct 2016 08:39:28 +0200 From: Michal Hocko Subject: Re: [PATCH 1/2] mm: memcontrol: use special workqueue for creating per-memcg caches Message-ID: <20161021063928.GC6045@dhcp22.suse.cz> References: <20161003120641.GC26768@dhcp22.suse.cz> <20161003123505.GA1862@esperanza> <20161003131930.GE26768@dhcp22.suse.cz> <20161004131417.GC1862@esperanza> <20161020204435.5e0ffca43c7b6ab5f69d692a@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161020204435.5e0ffca43c7b6ab5f69d692a@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Vladimir Davydov , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu 20-10-16 20:44:35, Andrew Morton wrote: > On Tue, 4 Oct 2016 16:14:17 +0300 Vladimir Davydov wrote: > > > Creating a lot of cgroups at the same time might stall all worker > > threads with kmem cache creation works, because kmem cache creation is > > done with the slab_mutex held. The problem was amplified by commits > > 801faf0db894 ("mm/slab: lockless decision to grow cache") in case of > > SLAB and 81ae6d03952c ("mm/slub.c: replace kick_all_cpus_sync() with > > synchronize_sched() in kmem_cache_shrink()") in case of SLUB, which > > increased the maximal time the slab_mutex can be held. > > > > To prevent that from happening, let's use a special ordered single > > threaded workqueue for kmem cache creation. This shouldn't introduce any > > functional changes regarding how kmem caches are created, as the work > > function holds the global slab_mutex during its whole runtime anyway, > > making it impossible to run more than one work at a time. By using a > > single threaded workqueue, we just avoid creating a thread per each > > work. Ordering is required to avoid a situation when a cgroup's work is > > put off indefinitely because there are other cgroups to serve, in other > > words to guarantee fairness. > > I'm having trouble working out the urgency of this patch? Seeing thousands of kernel threads is certainly annoying so I think we want to merge it sooner rather than later and have it backported to stable as well. -- Michal Hocko SUSE Labs -- 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