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 22DFCC433F5 for ; Wed, 30 Mar 2022 06:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243475AbiC3G4W (ORCPT ); Wed, 30 Mar 2022 02:56:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46466 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243480AbiC3G4N (ORCPT ); Wed, 30 Mar 2022 02:56:13 -0400 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF7FFC6EC9 for ; Tue, 29 Mar 2022 23:54:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1648623260; x=1680159260; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=VDubrcJ+t/HcriuuOM+0EmGnOACs+PPtNfGVh1oRR0o=; b=h7iHS1AFga/UTygm+M1L4Rs/RmYnd7PZaqaOTrgkfzmiZlUm7/e2ViXU ROfd50g5v4YJ0tniRDaN9j8UQztryh6AMnOLt2gZmiNgmDlr2zep3ojBZ 1TRqh1Ck33HsXRYByPd67DItUWENpC7e0mcZXaWo3OFE29hpko+m3AEM5 atW3Top9vgYf3d4Ay+iK6PSTo3BHXVEKBfVHwnd1NMRzGyZSBXHQe1iIG MaU6MYgc7QjMLRx1oUBHf5/vLXYCe5rz9v+2pJf55AhlLnuoVgF0IehZ+ GBg9EUlTaHXbs5WKrucYsxjjCoNtE7U2RyYnUvTyZLIWXfkiPMBlZfaFN A==; X-IronPort-AV: E=McAfee;i="6200,9189,10301"; a="284367738" X-IronPort-AV: E=Sophos;i="5.90,222,1643702400"; d="scan'208";a="284367738" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Mar 2022 23:54:19 -0700 X-IronPort-AV: E=Sophos;i="5.90,222,1643702400"; d="scan'208";a="565342016" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.239.13.94]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Mar 2022 23:54:16 -0700 From: "Huang, Ying" To: Baolin Wang Cc: Jagdish Gediya , , , , , Subject: Re: [PATCH] mm: migrate: set demotion targets differently References: <20220329115222.8923-1-jvgediya@linux.ibm.com> <784aee91-6a01-6e67-389e-1e1883796894@linux.alibaba.com> Date: Wed, 30 Mar 2022 14:54:14 +0800 In-Reply-To: <784aee91-6a01-6e67-389e-1e1883796894@linux.alibaba.com> (Baolin Wang's message of "Wed, 30 Mar 2022 14:37:35 +0800") Message-ID: <87lewsc4mh.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 Baolin Wang writes: > On 3/29/2022 10:04 PM, Jagdish Gediya wrote: >> On Tue, Mar 29, 2022 at 08:26:05PM +0800, Baolin Wang wrote: >> Hi Baolin, >>> Hi Jagdish, >>> >>> On 3/29/2022 7:52 PM, Jagdish Gediya wrote: >>>> The current implementation to identify the demotion >>>> targets limits some of the opportunities to share >>>> the demotion targets between multiple source nodes. >>>> >>>> Implement a logic to identify the loop in the demotion >>>> targets such that all the possibilities of demotion can >>>> be utilized. Don't share the used targets between all >>>> the nodes, instead create the used targets from scratch >>>> for each individual node based on for what all node this >>>> node is a demotion target. This helps to share the demotion >>>> targets without missing any possible way of demotion. >>>> >>>> e.g. with below NUMA topology, where node 0 & 1 are >>>> cpu + dram nodes, node 2 & 3 are equally slower memory >>>> only nodes, and node 4 is slowest memory only node, >>>> >>>> available: 5 nodes (0-4) >>>> node 0 cpus: 0 1 >>>> node 0 size: n MB >>>> node 0 free: n MB >>>> node 1 cpus: 2 3 >>>> node 1 size: n MB >>>> node 1 free: n MB >>>> node 2 cpus: >>>> node 2 size: n MB >>>> node 2 free: n MB >>>> node 3 cpus: >>>> node 3 size: n MB >>>> node 3 free: n MB >>>> node 4 cpus: >>>> node 4 size: n MB >>>> node 4 free: n MB >>>> node distances: >>>> node 0 1 2 3 4 >>>> 0: 10 20 40 40 80 >>>> 1: 20 10 40 40 80 >>>> 2: 40 40 10 40 80 >>>> 3: 40 40 40 10 80 >>>> 4: 80 80 80 80 10 >>>> >>>> The existing implementation gives below demotion targets, >>>> >>>> node demotion_target >>>> 0 3, 2 >>>> 1 4 >>>> 2 X >>>> 3 X >>>> 4 X >>>> >>>> With this patch applied, below are the demotion targets, >>>> >>>> node demotion_target >>>> 0 3, 2 >>>> 1 3, 2 >>>> 2 3 >>>> 3 4 >>>> 4 X >>> >>> Node 2 and node 3 both are slow memory and have same distance, why node 2 >>> should demote cold memory to node 3? They should have the same target >>> demotion node 4, which is the slowest memory node, right? >>> >> Current demotion target finding algorithm works based on best distance, as distance between node 2 & 3 is 40 and distance between node 2 & 4 is 80, node 2 demotes to node 3. > > If node 2 can demote to node 3, which means node 3's memory is colder > than node 2, right? The accessing time of node 3 should be larger than > node 2, then we can demote colder memory to node 3 from node 2. > > But node 2 and node 3 are same memory type and have same distance, the > accessing time of node 2 and node 3 should be same too, so why add so > many page migration between node 2 and node 3? I'm still not sure the > benefits. > > Huang Ying and Dave, how do you think about this demotion targets? Yes. I think the demotion target of 2 should be 4, as in my another email in this thread. Demoting from 2 to 3 makes no sense. Best Regards, Huang, Ying [snip]