From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id C1A336B0292 for ; Tue, 25 Jul 2017 12:40:01 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id v76so8487218qka.5 for ; Tue, 25 Jul 2017 09:40:01 -0700 (PDT) Received: from mail-qk0-x230.google.com (mail-qk0-x230.google.com. [2607:f8b0:400d:c09::230]) by mx.google.com with ESMTPS id i40si12000530qkh.265.2017.07.25.09.40.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Jul 2017 09:40:01 -0700 (PDT) Received: by mail-qk0-x230.google.com with SMTP id d145so65458502qkc.2 for ; Tue, 25 Jul 2017 09:40:00 -0700 (PDT) Date: Tue, 25 Jul 2017 12:39:57 -0400 From: Tejun Heo Subject: Re: pcpu allocator on large NUMA machines Message-ID: <20170725163957.GA3216015@devbig577.frc2.facebook.com> References: <20170724134240.GL25221@dhcp22.suse.cz> <20170724135714.GA3240919@devbig577.frc2.facebook.com> <20170724142826.GN25221@dhcp22.suse.cz> <877eyxz4r8.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <877eyxz4r8.fsf@concordia.ellerman.id.au> Sender: owner-linux-mm@kvack.org List-ID: To: Michael Ellerman Cc: Michal Hocko , Jiri Kosina , linux-mm@kvack.org, LKML Hello, Michael. On Tue, Jul 25, 2017 at 11:26:03AM +1000, Michael Ellerman wrote: > I don't think we want to stop using embed first chunk unless we have to. > > We have code that accesses percpu variables in real mode (with the MMU > off), and that wouldn't work easily if the first chunk wasn't in the > linear mapping. So it's not just an optimisation for us. > > We can fairly easily make the vmalloc space 56T, and I'm working on a > patch to make it ~500T on newer machines. Yeah, the only constraint is the size of vmalloc area in relation to the maximum spread across NUMA regions. If the vmalloc space can be made bigger, that'd be the best option. As the area percpu allocator actually uses is very small comparatively, it doesn't have to be a lot larger either. Thanks. -- tejun -- 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