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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=no 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 11826C3F2CF for ; Fri, 28 Feb 2020 03:38:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD61D24690 for ; Fri, 28 Feb 2020 03:38:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730797AbgB1Dih (ORCPT ); Thu, 27 Feb 2020 22:38:37 -0500 Received: from mga09.intel.com ([134.134.136.24]:36522 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730586AbgB1Dih (ORCPT ); Thu, 27 Feb 2020 22:38:37 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Feb 2020 19:38:37 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,493,1574150400"; d="scan'208";a="232107346" Received: from yhuang-dev.sh.intel.com ([10.239.159.23]) by orsmga008.jf.intel.com with ESMTP; 27 Feb 2020 19:38:33 -0800 From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , David Hildenbrand , Mel Gorman , Vlastimil Babka , Zi Yan , Michal Hocko , Peter Zijlstra , Dave Hansen , Minchan Kim , Johannes Weiner , Hugh Dickins Subject: [RFC 0/3] mm: Discard lazily freed pages when migrating Date: Fri, 28 Feb 2020 11:38:16 +0800 Message-Id: <20200228033819.3857058-1-ying.huang@intel.com> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Huang Ying MADV_FREE is a lazy free mechanism in Linux. According to the manpage of mavise(2), the semantics of MADV_FREE is, The application no longer requires the pages in the range specified by addr and len. The kernel can thus free these pages, but the freeing could be delayed until memory pressure occurs. ... Originally, the pages freed lazily by MADV_FREE will only be freed really by page reclaiming when there is memory pressure or when unmapping the address range. In addition to that, there's another opportunity to free these pages really, when we try to migrate them. The main value to do that is to avoid to create the new memory pressure immediately if possible. Instead, even if the pages are required again, they will be allocated gradually on demand. That is, the memory will be allocated lazily when necessary. This follows the common philosophy in the Linux kernel, allocate resources lazily on demand. This patchset implement this in addition to some cleanup to migration and MADV_FREE code. Best Regards, Huang, Ying