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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 06C3FC433B4 for ; Tue, 6 Apr 2021 16:42:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6A346613D8 for ; Tue, 6 Apr 2021 16:42:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A346613D8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id ECC476B007D; Tue, 6 Apr 2021 12:42:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EA3A56B0080; Tue, 6 Apr 2021 12:42:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CF5CE6B0081; Tue, 6 Apr 2021 12:42:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0163.hostedemail.com [216.40.44.163]) by kanga.kvack.org (Postfix) with ESMTP id B20D06B007D for ; Tue, 6 Apr 2021 12:42:21 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 6D41F8249980 for ; Tue, 6 Apr 2021 16:42:21 +0000 (UTC) X-FDA: 78002510082.28.D279E46 Received: from mail-ej1-f48.google.com (mail-ej1-f48.google.com [209.85.218.48]) by imf30.hostedemail.com (Postfix) with ESMTP id E6A50E000105 for ; Tue, 6 Apr 2021 16:42:15 +0000 (UTC) Received: by mail-ej1-f48.google.com with SMTP id n2so16747429ejy.7 for ; Tue, 06 Apr 2021 09:42:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5FhGpD+W2qCTNTtz8r16NI+eTTgYQsJqj2294KSTYfg=; b=O4mar5EJsHEnN3WGZVxrUQ0F0XF3kFlnGht20zddufgJZ7os++IvA0hgydkU4xbSDQ +XOriaf9ISSqRf2vVB6revLl0hdy3av+65Kpxdkm41s2St9tXkPlSkBFkXx9bD1szhiU wAspPAqPqAJsB9yRyIdy2/wZiflyFFxX0hzQPBIYIeGygO1XSMRBIJgwswmMKiS+sWFG yF4ii2tYVlWWmwTVszEJK+vomRUD+tgLYq/KTzKtdalo8kPxU43JfVp4wmAfvaAddN+C sP1K3RjL47NtXKKgky14aXscPq4mLN4XpNnLldlxuVStWnpAAoFPreeXMyNLUzYcz+6T ntYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5FhGpD+W2qCTNTtz8r16NI+eTTgYQsJqj2294KSTYfg=; b=PXgdF9P9x0tQnof1aAOA443f3mmLJqVyrbUgzPUe6Jmwt8tpnyWqNRNEUBErEFdvS9 7lYZQZM8fm8uwNucME3aLCT9wzAn6G5xEvRkOA+ybF8PKUzvnBCzJ72jsKAFyezqJ4b2 AjUWiLnJ6MICExPHvEN7nl9RboZZoEawBrc1yyJIK2xbcAzlFTbdohLUileLPDeSC8n1 1YJYPrOBTzTn2HnI6SMjmWkVxHuWmo+ZKpW2lKlutbkbhB7wQha+UYDmvPmv7SEmxgC5 qHe5D82yiMLrD1HlUwAnA/GTJweY89uWrHjioqvRK5wNGAqCZnDuXxggUmDp9MZtr9R/ g0uA== X-Gm-Message-State: AOAM532nGG/Yh8XjYBD8xCfoUgUe2lgErkgEopo2geP4NwHjTuAs/T4P FnTnEs+UXJCn10gOH6L7chsSZR1qHDbI8WoJRZk= X-Google-Smtp-Source: ABdhPJzGmpH9vtOSzDZ4/Y4obgIO+geB2MftQxr3dsbqxdiL5KplV4MIvAmDjQLurBc4ZwCpMsr6uQPYr8rBQRgCd0g= X-Received: by 2002:a17:906:b296:: with SMTP id q22mr13134681ejz.161.1617727339539; Tue, 06 Apr 2021 09:42:19 -0700 (PDT) MIME-Version: 1.0 References: <20210329183312.178266-1-shy828301@gmail.com> <20210330164200.01a4b78f@thinkpad> <20210331134727.47bc1e6d@thinkpad> <20210406140251.2779c400@thinkpad> In-Reply-To: <20210406140251.2779c400@thinkpad> From: Yang Shi Date: Tue, 6 Apr 2021 09:42:07 -0700 Message-ID: Subject: Re: [RFC PATCH 0/6] mm: thp: use generic THP migration for NUMA hinting fault To: Gerald Schaefer Cc: Mel Gorman , "Kirill A. Shutemov" , Zi Yan , Michal Hocko , Huang Ying , Hugh Dickins , hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, Andrew Morton , Linux MM , linux-s390@vger.kernel.org, Linux Kernel Mailing List , Alexander Gordeev Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E6A50E000105 X-Stat-Signature: 7efcbhxzopm6tkrwpoba5z3kjru949ow Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf30; identity=mailfrom; envelope-from=""; helo=mail-ej1-f48.google.com; client-ip=209.85.218.48 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617727335-39496 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Apr 6, 2021 at 5:03 AM Gerald Schaefer wrote: > > On Thu, 1 Apr 2021 13:10:49 -0700 > Yang Shi wrote: > > [...] > > > > > > > > Yes, it could be. The old behavior of migration was to return -ENOMEM > > > > if THP migration is not supported then split THP. That behavior was > > > > not very friendly to some usecases, for example, memory policy and > > > > migration lieu of reclaim (the upcoming). But I don't mean we restore > > > > the old behavior. We could split THP if it returns -ENOSYS and the > > > > page is THP. > > > > > > OK, as long as we don't get any broken PMD migration entries established > > > for s390, some extra THP splitting would be acceptable I guess. > > > > There will be no migration PMD installed. The current behavior is a > > no-op if THP migration is not supported. > > Ok, just for completeness, since Mel also replied that the split > was not done on other architectures "because the loss from splitting > exceeded the gain of improved locality": > > I did not mean to request extra splitting functionality for s390, > simply skipping / ignoring large PMDs would also be fine for s390, > no need to add extra complexity. Thank you. It could make life easier. The current code still converts huge PMD to RPOTNONE even though THP migration is not supported. It is easy to skip such PMDs hence cycles are saved for pointless NUMA hinting page faults. Will do so in v2 if no objection from Mel as well.