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=unavailable 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 CF29AC04FF3 for ; Mon, 24 May 2021 05:55:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 576ED61139 for ; Mon, 24 May 2021 05:55:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 576ED61139 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2842794004A; Mon, 24 May 2021 01:55:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 22F74940042; Mon, 24 May 2021 01:55:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C907C94004A; Mon, 24 May 2021 01:55:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0190.hostedemail.com [216.40.44.190]) by kanga.kvack.org (Postfix) with ESMTP id 8AC30940042 for ; Mon, 24 May 2021 01:55:55 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0F3745823 for ; Mon, 24 May 2021 05:55:55 +0000 (UTC) X-FDA: 78175063470.02.8634579 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by imf29.hostedemail.com (Postfix) with ESMTP id D07732CF for ; Mon, 24 May 2021 05:55:46 +0000 (UTC) IronPort-SDR: SI4IX7Sibuzi73nRkGvvf6Jd/GZgz9NhJAW+fT8KiWY4yzVKVV35stspDY8BxySrWzb0KVFIRq WfI+6BSvE/Sw== X-IronPort-AV: E=McAfee;i="6200,9189,9993"; a="198802604" X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="198802604" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.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) Authentication-Results: imf29.hostedemail.com; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none); spf=none (imf29.hostedemail.com: domain of feng.tang@intel.com has no SPF policy when checking 192.55.52.93) smtp.mailfrom=feng.tang@intel.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D07732CF X-Stat-Signature: y4ki51imghhjn9hssr43tbpk1mhtoqj3 X-HE-Tag: 1621835746-221880 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > > > >