From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A3D2C433FE for ; Tue, 29 Nov 2022 15:17:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234734AbiK2PRS (ORCPT ); Tue, 29 Nov 2022 10:17:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44008 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234059AbiK2PRQ (ORCPT ); Tue, 29 Nov 2022 10:17:16 -0500 Received: from outbound-smtp51.blacknight.com (outbound-smtp51.blacknight.com [46.22.136.235]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D55C245EFD for ; Tue, 29 Nov 2022 07:17:14 -0800 (PST) Received: from mail.blacknight.com (pemlinmail02.blacknight.ie [81.17.254.11]) by outbound-smtp51.blacknight.com (Postfix) with ESMTPS id 20E72FA9DE for ; Tue, 29 Nov 2022 15:17:13 +0000 (GMT) Received: (qmail 3308 invoked from network); 29 Nov 2022 15:17:12 -0000 Received: from unknown (HELO morpheus.112glenside.lan) (mgorman@techsingularity.net@[84.203.198.246]) by 81.17.254.9 with ESMTPA; 29 Nov 2022 15:17:12 -0000 From: Mel Gorman To: Linux-MM Cc: Andrew Morton , Michal Hocko , NeilBrown , Thierry Reding , Matthew Wilcox , Vlastimil Babka , LKML , Mel Gorman Subject: [RFC PATCH 0/6] Discard __GFP_ATOMIC Date: Tue, 29 Nov 2022 15:16:55 +0000 Message-Id: <20221129151701.23261-1-mgorman@techsingularity.net> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Neil's patch has been residing in mm-unstable as commit 2fafb4fe8f7a ("mm: discard __GFP_ATOMIC") for a long time and recently brought up again. Most recently, I was worried that __GFP_HIGH allocations could use high-order atomic reserves which is unintentional but there was no response so lets revisit -- this series reworks how min reserves are used, protects highorder reserves and then finishes with Neil's patch with very minor modifications so it fits on top. There was a review discussion on renaming __GFP_DIRECT_RECLAIM to __GFP_ALLOW_BLOCKING but I didn't think it was that big an issue and is ortogonal to the removal of __GFP_ATOMIC. There were some concerns about how the gfp flags affect the min reserves but it never reached a solid conclusion so I made my own attempt. The series tries to iron out some of the details on how reserves are used. ALLOC_HIGH becomes ALLOC_MIN_RESERVE and ALLOC_HARDER becomes ALLOC_NON_BLOCK and documents how the reserves are affected. For example, ALLOC_NON_BLOCK (no direct reclaim) on its own allows 25% of the min reserve. ALLOC_MIN_RESERVE (__GFP_HIGH) allows 50% and both combined allows deeper access again. ALLOC_OOM allows access to 75%. High-order atomic allocations are explicitly handled with the caveat that no __GFP_ATOMIC flag means that any high-order allocation that specifies GFP_HIGH and cannot enter direct reclaim will be treated as if it was GFP_ATOMIC. -- 2.35.3