From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: Re: [RFC 1/2] Protect larger order pages from breaking up Date: Fri, 16 Feb 2018 13:08:11 -0800 Message-ID: <7fcd53ab-ba06-f80e-6cb7-73e87bcbdd20@intel.com> References: <20180216160110.641666320@linux.com> <20180216160121.519788537@linux.com> <87d2edf7-ce5e-c643-f972-1f2538208d86@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christopher Lameter Cc: Mel Gorman , Matthew Wilcox , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, Thomas Schoebel-Theuer , andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org, Rik van Riel , Michal Hocko , Guy Shattah , Anshuman Khandual , Michal Nazarewicz , Vlastimil Babka , David Nellans , Laura Abbott , Pavel Machek , Mike Kravetz List-Id: linux-rdma@vger.kernel.org On 02/16/2018 12:15 PM, Christopher Lameter wrote: >> This has the potential to be really confusing to apps. If this memory >> is now not available to normal apps, they might plow into the invisible >> memory limits and get into nasty reclaim scenarios. >> Shouldn't this subtract the memory for MemFree and friends? > Ok certainly we could do that. But on the other hand the memory is > available if those subsystems ask for the right order. Its not clear to me > what the right way of handling this is. Right now it adds the reserved > pages to the watermarks. But then under some circumstances the memory is > available. What is the best solution here? There's definitely no perfect solution. But, in general, I think we should cater to the dumbest users. Folks doing higher-order allocations are not that. I say we make the picture the most clear for the traditional 4k users. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f71.google.com (mail-pl0-f71.google.com [209.85.160.71]) by kanga.kvack.org (Postfix) with ESMTP id 776786B0006 for ; Fri, 16 Feb 2018 16:08:14 -0500 (EST) Received: by mail-pl0-f71.google.com with SMTP id n11so2956311plp.13 for ; Fri, 16 Feb 2018 13:08:14 -0800 (PST) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTPS id a33-v6si220752pld.653.2018.02.16.13.08.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Feb 2018 13:08:13 -0800 (PST) Subject: Re: [RFC 1/2] Protect larger order pages from breaking up References: <20180216160110.641666320@linux.com> <20180216160121.519788537@linux.com> <87d2edf7-ce5e-c643-f972-1f2538208d86@intel.com> From: Dave Hansen Message-ID: <7fcd53ab-ba06-f80e-6cb7-73e87bcbdd20@intel.com> Date: Fri, 16 Feb 2018 13:08:11 -0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christopher Lameter Cc: Mel Gorman , Matthew Wilcox , linux-mm@kvack.org, linux-rdma@vger.kernel.org, akpm@linux-foundation.org, Thomas Schoebel-Theuer , andi@firstfloor.org, Rik van Riel , Michal Hocko , Guy Shattah , Anshuman Khandual , Michal Nazarewicz , Vlastimil Babka , David Nellans , Laura Abbott , Pavel Machek , Mike Kravetz On 02/16/2018 12:15 PM, Christopher Lameter wrote: >> This has the potential to be really confusing to apps. If this memory >> is now not available to normal apps, they might plow into the invisible >> memory limits and get into nasty reclaim scenarios. >> Shouldn't this subtract the memory for MemFree and friends? > Ok certainly we could do that. But on the other hand the memory is > available if those subsystems ask for the right order. Its not clear to me > what the right way of handling this is. Right now it adds the reserved > pages to the watermarks. But then under some circumstances the memory is > available. What is the best solution here? There's definitely no perfect solution. But, in general, I think we should cater to the dumbest users. Folks doing higher-order allocations are not that. I say we make the picture the most clear for the traditional 4k users. -- 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