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 20C49C67871 for ; Thu, 27 Oct 2022 07:46:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234367AbiJ0HqA (ORCPT ); Thu, 27 Oct 2022 03:46:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233565AbiJ0Hp5 (ORCPT ); Thu, 27 Oct 2022 03:45:57 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5DD4C8E71D; Thu, 27 Oct 2022 00:45:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1666856756; x=1698392756; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=OCW40ZbCm1Tk3tTV/GsPHE+LH/8n92DVVvxKQTSwmrw=; b=FY+s2jVshivBRu8478Wu0wi3PCfaiz6rqsSrGkNddpS7ZrIhgV/67fus /5Lw/mxBOT/HNo1BrUwjP8SXYmKMX1+3bo+S3JNS9rc3k6/vTY8p58OeZ x5wdOc4BHRfvU1hp+mp0QXaAz/Na8Ae48Mu9akTLrxH89K6It0xl+e+zb kIaCD8VF/uRiOObewR4+VKBEjYxAKqU62Au+Gok65XDKEOGf1dloPg/Yv USMqOZ36arwy3T/QbaNkRoBRTjzXP7m4tCKIrArFdaFZfVEUXInaILGs6 bNFG7i272DVrmiiyrECfiY+4S+WgLkwa174Z8ZBZrUajONo4QEm1IVew2 g==; X-IronPort-AV: E=McAfee;i="6500,9779,10512"; a="309247706" X-IronPort-AV: E=Sophos;i="5.95,217,1661842800"; d="scan'208";a="309247706" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Oct 2022 00:45:55 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10512"; a="610259267" X-IronPort-AV: E=Sophos;i="5.95,217,1661842800"; d="scan'208";a="610259267" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Oct 2022 00:45:52 -0700 From: "Huang, Ying" To: Feng Tang Cc: Yang Shi , "Hocko, Michal" , Aneesh Kumar K V , Andrew Morton , Johannes Weiner , Tejun Heo , Zefan Li , Waiman Long , "linux-mm@kvack.org" , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Hansen, Dave" , "Chen, Tim C" , "Yin, Fengwei" Subject: Re: [PATCH] mm/vmscan: respect cpuset policy during page demotion References: <20221026074343.6517-1-feng.tang@intel.com> Date: Thu, 27 Oct 2022 15:45:12 +0800 In-Reply-To: (Feng Tang's message of "Thu, 27 Oct 2022 15:11:53 +0800") Message-ID: <87k04lk8vr.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Feng Tang writes: > On Thu, Oct 27, 2022 at 01:57:52AM +0800, Yang Shi wrote: >> On Wed, Oct 26, 2022 at 8:59 AM Michal Hocko wrote: > [...] >> > > > This all can get quite expensive so the primary question is, does the >> > > > existing behavior generates any real issues or is this more of an >> > > > correctness exercise? I mean it certainly is not great to demote to an >> > > > incompatible numa node but are there any reasonable configurations when >> > > > the demotion target node is explicitly excluded from memory >> > > > policy/cpuset? >> > > >> > > We haven't got customer report on this, but there are quite some customers >> > > use cpuset to bind some specific memory nodes to a docker (You've helped >> > > us solve a OOM issue in such cases), so I think it's practical to respect >> > > the cpuset semantics as much as we can. >> > >> > Yes, it is definitely better to respect cpusets and all local memory >> > policies. There is no dispute there. The thing is whether this is really >> > worth it. How often would cpusets (or policies in general) go actively >> > against demotion nodes (i.e. exclude those nodes from their allowes node >> > mask)? >> > >> > I can imagine workloads which wouldn't like to get their memory demoted >> > for some reason but wouldn't it be more practical to tell that >> > explicitly (e.g. via prctl) rather than configuring cpusets/memory >> > policies explicitly? >> > >> > > Your concern about the expensive cost makes sense! Some raw ideas are: >> > > * if the shrink_folio_list is called by kswapd, the folios come from >> > > the same per-memcg lruvec, so only one check is enough >> > > * if not from kswapd, like called form madvise or DAMON code, we can >> > > save a memcg cache, and if the next folio's memcg is same as the >> > > cache, we reuse its result. And due to the locality, the real >> > > check is rarely performed. >> > >> > memcg is not the expensive part of the thing. You need to get from page >> > -> all vmas::vm_policy -> mm -> task::mempolicy >> >> Yeah, on the same page with Michal. Figuring out mempolicy from page >> seems quite expensive and the correctness can't be guranteed since the >> mempolicy could be set per-thread and the mm->task depends on >> CONFIG_MEMCG so it doesn't work for !CONFIG_MEMCG. > > Yes, you are right. Our "working" psudo code for mem policy looks like > what Michal mentioned, and it can't work for all cases, but try to > enforce it whenever possible: > > static bool __check_mpol_demotion(struct folio *folio, struct vm_area_struct *vma, > unsigned long addr, void *arg) > { > bool *skip_demotion = arg; > struct mempolicy *mpol; > int nid, dnid; > bool ret = true; > > mpol = __get_vma_policy(vma, addr); > if (!mpol) { > struct task_struct *task; task = NULL; > if (vma->vm_mm) > task = vma->vm_mm->owner; > > if (task) { > mpol = get_task_policy(task); > if (mpol) > mpol_get(mpol); > } > } > > if (!mpol) > return ret; > > if (mpol->mode != MPOL_BIND) > goto put_exit; > > nid = folio_nid(folio); > dnid = next_demotion_node(nid); > if (!node_isset(dnid, mpol->nodes)) { > *skip_demotion = true; > ret = false; > } I think that you need to get a node mask instead. Even if !node_isset(dnid, mpol->nodes), you may demote to other node in the node mask. Best Regards, Huang, Ying > > put_exit: > mpol_put(mpol); > return ret; > } > > static unsigned int shrink_page_list(struct list_head *page_list,..) > { > ... > > bool skip_demotion = false; > struct rmap_walk_control rwc = { > .arg = &skip_demotion, > .rmap_one = __check_mpol_demotion, > }; > > /* memory policy check */ > rmap_walk(folio, &rwc); > if (skip_demotion) > goto keep_locked; > } > > And there seems to be no simple solution for getting the memory > policy from a page. > > Thanks, > Feng > >> > >> > -- >> > Michal Hocko >> > SUSE Labs >> > >> From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Huang, Ying" Subject: Re: [PATCH] mm/vmscan: respect cpuset policy during page demotion Date: Thu, 27 Oct 2022 15:45:12 +0800 Message-ID: <87k04lk8vr.fsf@yhuang6-desk2.ccr.corp.intel.com> References: <20221026074343.6517-1-feng.tang@intel.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1666856756; x=1698392756; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=OCW40ZbCm1Tk3tTV/GsPHE+LH/8n92DVVvxKQTSwmrw=; b=FY+s2jVshivBRu8478Wu0wi3PCfaiz6rqsSrGkNddpS7ZrIhgV/67fus /5Lw/mxBOT/HNo1BrUwjP8SXYmKMX1+3bo+S3JNS9rc3k6/vTY8p58OeZ x5wdOc4BHRfvU1hp+mp0QXaAz/Na8Ae48Mu9akTLrxH89K6It0xl+e+zb kIaCD8VF/uRiOObewR4+VKBEjYxAKqU62Au+Gok65XDKEOGf1dloPg/Yv USMqOZ36arwy3T/QbaNkRoBRTjzXP7m4tCKIrArFdaFZfVEUXInaILGs6 bNFG7i272DVrmiiyrECfiY+4S+WgLkwa174Z8ZBZrUajONo4QEm1IVew2 g==; In-Reply-To: (Feng Tang's message of "Thu, 27 Oct 2022 15:11:53 +0800") List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Feng Tang Cc: Yang Shi , "Hocko, Michal" , Aneesh Kumar K V , Andrew Morton , Johannes Weiner , Tejun Heo , Zefan Li , Waiman Long , "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" , "cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "Hansen, Dave" , "Chen, Tim C" , "Yin, Fengwei" Feng Tang writes: > On Thu, Oct 27, 2022 at 01:57:52AM +0800, Yang Shi wrote: >> On Wed, Oct 26, 2022 at 8:59 AM Michal Hocko wrote: > [...] >> > > > This all can get quite expensive so the primary question is, does the >> > > > existing behavior generates any real issues or is this more of an >> > > > correctness exercise? I mean it certainly is not great to demote to an >> > > > incompatible numa node but are there any reasonable configurations when >> > > > the demotion target node is explicitly excluded from memory >> > > > policy/cpuset? >> > > >> > > We haven't got customer report on this, but there are quite some customers >> > > use cpuset to bind some specific memory nodes to a docker (You've helped >> > > us solve a OOM issue in such cases), so I think it's practical to respect >> > > the cpuset semantics as much as we can. >> > >> > Yes, it is definitely better to respect cpusets and all local memory >> > policies. There is no dispute there. The thing is whether this is really >> > worth it. How often would cpusets (or policies in general) go actively >> > against demotion nodes (i.e. exclude those nodes from their allowes node >> > mask)? >> > >> > I can imagine workloads which wouldn't like to get their memory demoted >> > for some reason but wouldn't it be more practical to tell that >> > explicitly (e.g. via prctl) rather than configuring cpusets/memory >> > policies explicitly? >> > >> > > Your concern about the expensive cost makes sense! Some raw ideas are: >> > > * if the shrink_folio_list is called by kswapd, the folios come from >> > > the same per-memcg lruvec, so only one check is enough >> > > * if not from kswapd, like called form madvise or DAMON code, we can >> > > save a memcg cache, and if the next folio's memcg is same as the >> > > cache, we reuse its result. And due to the locality, the real >> > > check is rarely performed. >> > >> > memcg is not the expensive part of the thing. You need to get from page >> > -> all vmas::vm_policy -> mm -> task::mempolicy >> >> Yeah, on the same page with Michal. Figuring out mempolicy from page >> seems quite expensive and the correctness can't be guranteed since the >> mempolicy could be set per-thread and the mm->task depends on >> CONFIG_MEMCG so it doesn't work for !CONFIG_MEMCG. > > Yes, you are right. Our "working" psudo code for mem policy looks like > what Michal mentioned, and it can't work for all cases, but try to > enforce it whenever possible: > > static bool __check_mpol_demotion(struct folio *folio, struct vm_area_struct *vma, > unsigned long addr, void *arg) > { > bool *skip_demotion = arg; > struct mempolicy *mpol; > int nid, dnid; > bool ret = true; > > mpol = __get_vma_policy(vma, addr); > if (!mpol) { > struct task_struct *task; task = NULL; > if (vma->vm_mm) > task = vma->vm_mm->owner; > > if (task) { > mpol = get_task_policy(task); > if (mpol) > mpol_get(mpol); > } > } > > if (!mpol) > return ret; > > if (mpol->mode != MPOL_BIND) > goto put_exit; > > nid = folio_nid(folio); > dnid = next_demotion_node(nid); > if (!node_isset(dnid, mpol->nodes)) { > *skip_demotion = true; > ret = false; > } I think that you need to get a node mask instead. Even if !node_isset(dnid, mpol->nodes), you may demote to other node in the node mask. Best Regards, Huang, Ying > > put_exit: > mpol_put(mpol); > return ret; > } > > static unsigned int shrink_page_list(struct list_head *page_list,..) > { > ... > > bool skip_demotion = false; > struct rmap_walk_control rwc = { > .arg = &skip_demotion, > .rmap_one = __check_mpol_demotion, > }; > > /* memory policy check */ > rmap_walk(folio, &rwc); > if (skip_demotion) > goto keep_locked; > } > > And there seems to be no simple solution for getting the memory > policy from a page. > > Thanks, > Feng > >> > >> > -- >> > Michal Hocko >> > SUSE Labs >> > >>