From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751395AbeEPUlo (ORCPT ); Wed, 16 May 2018 16:41:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:49256 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751033AbeEPUlo (ORCPT ); Wed, 16 May 2018 16:41:44 -0400 Subject: Re: [PATCH] mm: save two stranding bit in gfp_mask To: Shakeel Butt , Michal Hocko , Andrew Morton , Greg Thelen , Mel Gorman Cc: Linux MM , LKML References: <20180516202023.167627-1-shakeelb@google.com> From: Vlastimil Babka Message-ID: <90167afa-ecfb-c5ef-3554-ddb7e6ac9728@suse.cz> Date: Wed, 16 May 2018 22:39:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180516202023.167627-1-shakeelb@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/16/2018 10:20 PM, Shakeel Butt wrote: > ___GFP_COLD and ___GFP_OTHER_NODE were removed but their bits were > stranded. Slide existing gfp masks to make those two bits available. Well, there are already available for hypothetical new flags. Is there anything that benefits from a smaller __GFP_BITS_SHIFT? Otherwise no big objection, besides the churn. Maybe move the last (well, before NOLOCKDEP) two flags to the "holes" instead of shifting everything? That would be closer to what compaction does... There's also an ongoing effort to make the lowest 4 flags a number, would that mean more free bits and churn soon? I would also dislike having to learn new numbers for typical flag combinations to recognize them in oom reports/alloc failures, but somebody had the great idea to print those symbolically, so nevermind. Vlastimil > Signed-off-by: Shakeel Butt