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 D58AFC433EF for ; Fri, 18 Feb 2022 08:03:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231209AbiBRIEG (ORCPT ); Fri, 18 Feb 2022 03:04:06 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:44130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229977AbiBRIEA (ORCPT ); Fri, 18 Feb 2022 03:04:00 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C5752B2FFD for ; Fri, 18 Feb 2022 00:03:45 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A14F761299 for ; Fri, 18 Feb 2022 08:03:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62357C340E9; Fri, 18 Feb 2022 08:03:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645171424; bh=1fBC7GGSjQURm/YJ/N2eyc/koN7mPuNwXAIqCpJshIQ=; h=From:To:Cc:Subject:Date:In-Reply-To:From; b=VrXQ4IarbaSq+cKXFQjdKD/3DM8YR2Vo3FUlXSiOJlasS7m8fgxIWGqEBiHvW/ei3 L7YKgteVEhbctagLZLsppu/DQDOQoxy2qTtZsrCaJ8xtIZW/JCv4Ep2Y82kejdYQRf wrQBZIXXm+VGRjmfF/nAKLhgdxxbmCVUfR/oUTVuXH61RaTCiS8gA1i5v3PhhyYglF Cdsaf15VqKshWJP4cb/CiJvbOs9WKTPjElL1hevFic9xpdWV5p/6yW7O+AzU25AHSM WvcN5bYcVvwasctX6AK9GIVmb/3Eqo1lXwt0d6xJZpC+H+X+gGLaqn5munOzTU2TBw L3ICTCx2tkjRA== From: SeongJae Park To: Xin Hao Cc: SeongJae Park , rongwei.wang@linux.alibaba.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rientjes@google.com, linux-damon@amazon.com Subject: Re: [RFC PATCH V1 0/5] mm/damon: Add NUMA access statistics function support Date: Fri, 18 Feb 2022 08:03:40 +0000 Message-Id: <20220218080340.11566-1-sj@kernel.org> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 In-Reply-To: <503fa0b1-be20-a17e-72f0-14b38c0dc719@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 18 Feb 2022 10:21:27 +0800 Xin Hao wrote: > Hi SeongJae: > > On 2/17/22 4:29 PM, SeongJae Park wrote: > > + David Rientjes, who has shown interest[1] in this topic. > > > > [1] https://lore.kernel.org/linux-mm/bcc8d9a0-81d-5f34-5e4-fcc28eb7ce@google.com/ > > > > --- > > > > Hi Xin, > > > > > > Thank you always for great patches! > > > > On Wed, 16 Feb 2022 16:30:36 +0800 Xin Hao wrote: > > [...] > > I'd like to comment on the high level design at the moment. To my > > understanding, this patchset extends DAMON core and monitoring operations for > > virtual address spaces (vaddr) and the physical address space (paddr) to > > monitor NUMA-local/remote accesses via PROT_NONE and page faults mechanism. > > > > The underlying mechanism for NUMA-local/remote accesses (PROT_NONE and page > > fault) looks ok to me. But, changes to the core and vaddr/paddr operations > > looks unnecessary, to me. That's also not for general use cases. > You are right, adding NUMA access statistics does make the PA & VA codes > look confusing。 > > > > I think it would be simpler to implment more monitoring operations for NUMA > > monitoring use case (one for NUMA-local accesses accounting and another one for > > NUMA-remote accesses accounting), alongside vaddr and paddr. Then, users could > > configure DAMON to have three monitoring contexts (one with vaddr ops, second > > one with numa-local ops, and third one with numa-remote ops), run those > > concurrently, then show the three results and make some decisions like > > migrations. > > Thanks for your advice, I will implement these in the next version, But > from my understanding or maybe > > I didn't get what you were thinking, I think only one monitor context is > needed for NUMA Local & Remote, > > Do not need a separate implementation like "numa_local_ops" and > "numa_remote_ops", just set "numa_access_ops" is ok. Sorry for insufficient explanation of my concern. In short, I'm concerning about the regions adjustment. You may do so by storing NUMA-local access count and NUMA-remote access count in the nr_acceses filed of each region, e.g., saving NUMA-local access count in upper-half bits of nr_accesses and saving NUMA-remote access count in the lower-half bits. However, then DAMON will do the regions adjustment based on the NUMA-local/remote accesses count mixed value, so the accuracy would be degraded. So I think we need to implement each monitoring operations set for each accesses that we want to monitor. > > > > > One additional advantage of this approach is that the accuracy for > > NUMA-local/remote accessed could be better, because the contexts configured to > > use NUMA-local/remote monitoring ops will do the regions adjustment with > > NUMA-local/remote accesses (to my understanding, this patchset let regions have > > NUMA-local/remote accesses counter in addition to the total one, but still use > > only the total one for the regions adjustment). My previous comment above might help clarifying my concern. If I'm missing something, please let me know. Thanks, SJ > > > > If I'm missing something, please let me know. > > > > > > Thanks, > > SJ > > > >> -- > >> 2.27.0 > > -- > Best Regards! > Xin Hao >