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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 DEB2FC433E1 for ; Tue, 18 Aug 2020 18:48:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 86BDC206B5 for ; Tue, 18 Aug 2020 18:48:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726752AbgHRSsC (ORCPT ); Tue, 18 Aug 2020 14:48:02 -0400 Received: from mga06.intel.com ([134.134.136.31]:36697 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726576AbgHRSsB (ORCPT ); Tue, 18 Aug 2020 14:48:01 -0400 IronPort-SDR: IVDYX5Rb3CRXEL/nbryLP52dYXl5H6A4Jf0dzueeCWW9GkaQzyal3M06dhAB4el/zYBVoIowDG vwbj/ObYelqw== X-IronPort-AV: E=McAfee;i="6000,8403,9717"; a="216512912" X-IronPort-AV: E=Sophos;i="5.76,328,1592895600"; d="scan'208";a="216512912" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Aug 2020 11:48:01 -0700 IronPort-SDR: WIa7X/9iStEAYLjxD5dyLJm8cBF40k5hzdTqkxY+uoT8BBhOhJ645QlDpnn5hdNZBWEpEBzXpO MdV2IyLkKL9w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,328,1592895600"; d="scan'208";a="370983290" Received: from viggo.jf.intel.com (HELO localhost.localdomain) ([10.54.77.144]) by orsmga001.jf.intel.com with ESMTP; 18 Aug 2020 11:48:01 -0700 Subject: [RFC][PATCH 0/9] [v3] Migrate Pages in lieu of discard To: linux-kernel@vger.kernel.org Cc: Dave Hansen , yang.shi@linux.alibaba.com, rientjes@google.com, ying.huang@intel.com, dan.j.williams@intel.com From: Dave Hansen Date: Tue, 18 Aug 2020 11:41:22 -0700 Message-Id: <20200818184122.29C415DF@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org todo: Changes since (https://lwn.net/Articles/824830/): * Use higher-level migrate_pages() API approach from Yang Shi's earlier patches. * made sure to actually check node_reclaim_mode's new bit * disabled migration entirely before introducing RECLAIM_MIGRATE * Replace GFP_NOWAIT with explicit __GFP_KSWAPD_RECLAIM and comment why we want that. * Comment on effects of that keep multiple source nodes from sharing target nodes The full series is also available here: https://github.com/hansendc/linux/tree/automigrate-20200818 -- We're starting to see systems with more and more kinds of memory such as Intel's implementation of persistent memory. Let's say you have a system with some DRAM and some persistent memory. Today, once DRAM fills up, reclaim will start and some of the DRAM contents will be thrown out. Allocations will, at some point, start falling over to the slower persistent memory. That has two nasty properties. First, the newer allocations can end up in the slower persistent memory. Second, reclaimed data in DRAM are just discarded even if there are gobs of space in persistent memory that could be used. This set implements a solution to these problems. At the end of the reclaim process in shrink_page_list() just before the last page refcount is dropped, the page is migrated to persistent memory instead of being dropped. While I've talked about a DRAM/PMEM pairing, this approach would function in any environment where memory tiers exist. This is not perfect. It "strands" pages in slower memory and never brings them back to fast DRAM. Other things need to be built to promote hot pages back to DRAM. This is also all based on an upstream mechanism that allows persistent memory to be onlined and used as if it were volatile: http://lkml.kernel.org/r/20190124231441.37A4A305@viggo.jf.intel.com == Open Issues == * For cpusets and memory policies that restrict allocations to PMEM, is it OK to demote to PMEM? Do we need a cgroup- level API to opt-in or opt-out of these migrations? * Migration failures will result in pages being unreclaimable. Need to be able to fall back to normal reclaim. Cc: Yang Shi Cc: David Rientjes Cc: Huang Ying Cc: Dan Williams -- Dave Hansen (5): mm/numa: node demotion data structure and lookup mm/vmscan: Attempt to migrate page in lieu of discard mm/numa: automatically generate node migration order mm/vmscan: never demote for memcg reclaim mm/numa: new reclaim mode to enable reclaim-based migration Keith Busch (2): mm/migrate: Defer allocating new page until needed mm/vmscan: Consider anonymous pages without swap Yang Shi (1): mm/vmscan: add page demotion counter Documentation/admin-guide/sysctl/vm.rst | 9 include/linux/migrate.h | 6 include/linux/node.h | 9 include/linux/vm_event_item.h | 2 include/trace/events/migrate.h | 3 mm/debug.c | 1 mm/internal.h | 1 mm/migrate.c | 400 ++++++++++++++++++++++++++------ mm/page_alloc.c | 2 mm/vmscan.c | 88 ++++++- mm/vmstat.c | 2 11 files changed, 439 insertions(+), 84 deletions(-)