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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 D0A37C04FF3 for ; Mon, 24 May 2021 05:55:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F75B61153 for ; Mon, 24 May 2021 05:55:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232282AbhEXF5U (ORCPT ); Mon, 24 May 2021 01:57:20 -0400 Received: from mga01.intel.com ([192.55.52.88]:33767 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229733AbhEXF5T (ORCPT ); Mon, 24 May 2021 01:57:19 -0400 IronPort-SDR: 9+g1tvz6dvq4X3VziN0G8KhqOTs5hxzie4jEERQ+RoUy0AxB7SOopgSncvz/V9mFmTN8+tdpkd rT+ot8egapDQ== X-IronPort-AV: E=McAfee;i="6200,9189,9993"; a="223013736" X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="223013736" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 May 2021 22:55:51 -0700 IronPort-SDR: PivyM5cGpVb+S3bGUvM+XALFFw+T7T+dYvtAtW5DbYVR3y7Br3ZLPQWg3C/JhxmYWWkBd93oRX YnoJwNpk1CNw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="475690932" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.147.94]) by orsmga001.jf.intel.com with ESMTP; 23 May 2021 22:55:48 -0700 Date: Mon, 24 May 2021 13:55:47 +0800 From: Feng Tang To: David Rientjes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Michal Hocko , Andrea Arcangeli , Mel Gorman , Mike Kravetz , Randy Dunlap , Vlastimil Babka , Dave Hansen , Ben Widawsky , Andi Kleen , Dan Williams , ying.huang@intel.com Subject: Re: [RFC Patch v2 1/4] mm/mempolicy: skip nodemask intersect check for 'interleave' when oom Message-ID: <20210524055547.GA48704@shbuild999.sh.intel.com> References: <1621499404-67756-1-git-send-email-feng.tang@intel.com> <1621499404-67756-2-git-send-email-feng.tang@intel.com> <682c92e5-ccb3-4b76-1f56-617f8e6e8f2@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <682c92e5-ccb3-4b76-1f56-617f8e6e8f2@google.com> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi David, Thanks for the review! On Sun, May 23, 2021 at 10:15:00PM -0700, David Rientjes wrote: > On Thu, 20 May 2021, Feng Tang wrote: > > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > > index d79fa29..1964cca 100644 > > --- a/mm/mempolicy.c > > +++ b/mm/mempolicy.c > > @@ -2098,7 +2098,7 @@ bool init_nodemask_of_mempolicy(nodemask_t *mask) > > * > > * If tsk's mempolicy is "default" [NULL], return 'true' to indicate default > > * policy. Otherwise, check for intersection between mask and the policy > > - * nodemask for 'bind' or 'interleave' policy. For 'preferred' or 'local' > > + * nodemask for 'bind' policy. For 'interleave', 'preferred' or 'local' > > * policy, always return true since it may allocate elsewhere on fallback. > > * > > * Takes task_lock(tsk) to prevent freeing of its mempolicy. > > @@ -2111,29 +2111,13 @@ bool mempolicy_nodemask_intersects(struct task_struct *tsk, > > > > if (!mask) > > return ret; > > + > > task_lock(tsk); > > mempolicy = tsk->mempolicy; > > - if (!mempolicy) > > - goto out; > > - > > - switch (mempolicy->mode) { > > - case MPOL_PREFERRED: > > - /* > > - * MPOL_PREFERRED and MPOL_F_LOCAL are only preferred nodes to > > - * allocate from, they may fallback to other nodes when oom. > > - * Thus, it's possible for tsk to have allocated memory from > > - * nodes in mask. > > - */ > > - break; > > - case MPOL_BIND: > > - case MPOL_INTERLEAVE: > > + if (mempolicy && mempolicy->mode == MPOL_BIND) > > ret = nodes_intersects(mempolicy->v.nodes, *mask); > > If MPOL_INTERLEAVE is deemed only a suggestion, the same could be > considered true of MPOL_BIND intersection as well, no? IIUC, 'bind' and 'interleave' are different regarding memory allocation. In alloc_pages_vma(), there are: nmask = policy_nodemask(gfp, pol); preferred_nid = policy_node(gfp, pol, node); page = __alloc_pages(gfp, order, preferred_nid, nmask); mpol_cond_put(pol); and in plicy_nodemask(), only 'bind' policy may return its desired nodemask, while all other returns NULL including 'interleave'. And this 'NULL' enables the 'interleave' policy can get memory from other nodes than its nodemask. So when allocating memory, 'interleave' can get memory from all nodes. I did some experements which also confirm this. Thanks, Feng > > > - break; > > - default: > > - BUG(); > > - } > > -out: > > task_unlock(tsk); > > + > > return ret; > > } > > > > -- > > 2.7.4 > > > >