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 X-Spam-Level: X-Spam-Status: No, score=-14.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25C36C2D0F0 for ; Tue, 31 Mar 2020 13:16:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F07E2208E0 for ; Tue, 31 Mar 2020 13:16:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="w9G5xdSJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730877AbgCaNQj (ORCPT ); Tue, 31 Mar 2020 09:16:39 -0400 Received: from mail-qv1-f67.google.com ([209.85.219.67]:41905 "EHLO mail-qv1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730703AbgCaNQi (ORCPT ); Tue, 31 Mar 2020 09:16:38 -0400 Received: by mail-qv1-f67.google.com with SMTP id t4so6603588qvz.8 for ; Tue, 31 Mar 2020 06:16:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=lWOY1a83oyzd8Wyzxobl7iyPgPSxUcv8H4rfgpi9Go0=; b=w9G5xdSJi2pwxLkw+UUYa9uD0cxKepK7FyN8BvxBNr7Qf28I7LNKazNm+grZ85uOZ3 YUp0H2DrxVoI8h+nOVinbooeJqV2zQ511twVls7fYGH+dwXNRxXxr3T3VCoRZ5/DGzhD eyZwCzRDkNzu/rI9nxQFLCQ6LvJiGX5snuiD0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=lWOY1a83oyzd8Wyzxobl7iyPgPSxUcv8H4rfgpi9Go0=; b=d5wz7cHo3YljJpLZRhAUOdVOBeeYY2dH8r5SK1Ook2b0t6TmBLlVrQ+7MTbkt9gh60 vYqS1fWH/Lmt5xrNlyKWg/IXLgGSj3XnggZUrjo8I3MC/2jtNhCuzEu3CZS8KNlIv7LP GE3dcX52IxukTUSugsdCT96o5XTwTWcSPg4M1o4p9a6JOxADTDT9JhW66h+p7k+L8kw8 F2a1CaHkMphUeM6QkmBLoyhmIgPABzNvQy/GPyqR/GbPuMc5QYVbM5gi0CKvA+0Nrhad +8xKYcO07hi/2rweSnuVw711jiTRUsLWUopMG78d5aJq9UR6dtx+9bQmHWzCEZeyAb20 kQMw== X-Gm-Message-State: ANhLgQ3aimPOcQ3c285tFngWg7/6iiO6fpCguYTbbFg7YM6o9xQZbezg 4AVvm55oOPFwgwZLLMOcU68lUlQWXok= X-Google-Smtp-Source: ADFU+vtXVj0qnZ925oHCMNMkIOnLjNT9wF24VWwCVSa51Qddhb1QgyuPqNP67rntZT+wlEmt8BzhpQ== X-Received: by 2002:a0c:f7d0:: with SMTP id f16mr16609830qvo.206.1585660597163; Tue, 31 Mar 2020 06:16:37 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id l16sm13731476qtc.73.2020.03.31.06.16.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2020 06:16:36 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , linux-mm@kvack.org, rcu@vger.kernel.org, willy@infradead.org, peterz@infradead.org, neilb@suse.com, vbabka@suse.cz, mgorman@suse.de, Andrew Morton , Josh Triplett , Lai Jiangshan , Mathieu Desnoyers , "Paul E. McKenney" , Steven Rostedt Subject: [PATCH RFC] rcu/tree: Use GFP_MEMALLOC for alloc memory to free memory pattern Date: Tue, 31 Mar 2020 09:16:28 -0400 Message-Id: <20200331131628.153118-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.26.0.rc2.310.g2932bb562d-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In kfree_rcu() headless implementation (where the caller need not pass an rcu_head, but rather directly pass a pointer to an object), we have a fall-back where we allocate a rcu_head wrapper for the caller (not the common case). This brings the pattern of needing to allocate some memory to free some memory. Currently we use GFP_ATOMIC flag to try harder for this allocation, however the GFP_MEMALLOC flag is more tailored to this pattern. We need to try harder not only during atomic context, but also during non-atomic context anyway. So use the GFP_MEMALLOC flag instead. Also remove the __GFP_NOWARN flag simply because although we do have a synchronize_rcu() fallback for absolutely worst case, we still would like to not enter that path and atleast trigger a warning to the user. Cc: linux-mm@kvack.org Cc: rcu@vger.kernel.org Cc: willy@infradead.org Cc: peterz@infradead.org Cc: neilb@suse.com Cc: vbabka@suse.cz Cc: mgorman@suse.de Cc: Andrew Morton Signed-off-by: Joel Fernandes (Google) --- This patch is based on the (not yet upstream) code in: git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git (branch rcu/kfree) It is a follow-up to the posted series: https://lore.kernel.org/lkml/20200330023248.164994-1-joel@joelfernandes.org/ kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 4be763355c9fb..965deefffdd58 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3149,7 +3149,7 @@ static inline struct rcu_head *attach_rcu_head_to_object(void *obj) if (!ptr) ptr = kmalloc(sizeof(unsigned long *) + - sizeof(struct rcu_head), GFP_ATOMIC | __GFP_NOWARN); + sizeof(struct rcu_head), GFP_MEMALLOC); if (!ptr) return NULL; -- 2.26.0.rc2.310.g2932bb562d-goog