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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 B7819C3A59C for ; Fri, 16 Aug 2019 15:02:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7EBC92173B for ; Fri, 16 Aug 2019 15:02:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="isXsm8F7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727418AbfHPPCg (ORCPT ); Fri, 16 Aug 2019 11:02:36 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:33426 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727217AbfHPPCf (ORCPT ); Fri, 16 Aug 2019 11:02:35 -0400 Received: by mail-pg1-f193.google.com with SMTP id n190so3093816pgn.0 for ; Fri, 16 Aug 2019 08:02:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=80681125HOe1NksgS/XdMjl6WQzpX7RNekCUe4aCq/Y=; b=isXsm8F7NqAKGGb6PgZvvznUtwOOxSMgaDX8r1auxQi6T+0wWxvsKu4UQcEV7FvDTt /kmf9wFUT593QxhHVbPkM/7ZvZjp8zaFDhuhrjJ+2dg5VecyfRCTm6uVilNB1OMAxGYo N1lfcetsW5mFyCCoz5J48KjqJUImLeh/5uo3n9ZQYv3BfWPRiAUE5t5mBjNxh1Yd0VhN N8Nd3Prb9PbpWE0nzwWQl+oCkS0chyoW+Snfn4DQJiX813XuRnuAobYBX4dgIpvjjB6S Xrpz7AxrAEACdibYFHVh5Ic5UWw9FIRtqz6dQ2UnxYP/8Bl541fTpvkhBdrngiAd7303 Qp7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=80681125HOe1NksgS/XdMjl6WQzpX7RNekCUe4aCq/Y=; b=ZiTYdygurh99qROO2cgrE/3kWgmqkdqJ4BgFhvDfkNcOJpiW/EU/iAyDJCQWfcn2MU tNMUTDamlNCnzI8QeTXGlv/qmC0R8JvW4tTK2D3N1OOQSD4/Pa/a3ZF2QdaqcfyVbIRc 4K80pkdzwRWtm+0pN+KO1bMFcQgk7CrBEvLeBhWy2ffYMMTaGQ907kG50gXfmUNkAMqI fAYnLO+6IX8j0qrHRQswsNH0qI7xKOGHKPfPUJRbWRqwBMTz9Ye3Xp/TyoUff74MURii zonae9hf2qMmswgfb2zrfhRAWW3fVoVD0sP70nsazBNC3Hem9dGGa8P1VxKUCYAMndxW MYIA== X-Gm-Message-State: APjAAAUX7EwJ98tYseSsaE2OWHwdb6j8cGXg0H0nnqlr4x/XH7BFIa3/ GFWTqP9morL3O8pRgaE/zw== X-Google-Smtp-Source: APXvYqyYrWsBv+YFWGKWMSvAj/Y6YsQ7WRpo5y7EPvTeuwShnVq5fuYFBDU7SpfgE/kycdeUsjN79w== X-Received: by 2002:a17:90a:5207:: with SMTP id v7mr7332463pjh.127.1565967755090; Fri, 16 Aug 2019 08:02:35 -0700 (PDT) Received: from mypc ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id f12sm5339136pgq.52.2019.08.16.08.02.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Aug 2019 08:02:33 -0700 (PDT) Date: Fri, 16 Aug 2019 23:02:22 +0800 From: Pingfan Liu To: Jerome Glisse Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , Jan Kara , "Kirill A. Shutemov" , Michal Hocko , Mike Kravetz , Andrea Arcangeli , Matthew Wilcox , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] mm/migrate: see hole as invalid source page Message-ID: <20190816150222.GA10855@mypc> References: <1565078411-27082-1-git-send-email-kernelfans@gmail.com> <1565078411-27082-2-git-send-email-kernelfans@gmail.com> <20190815172222.GD30916@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190815172222.GD30916@redhat.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 15, 2019 at 01:22:22PM -0400, Jerome Glisse wrote: > On Tue, Aug 06, 2019 at 04:00:10PM +0800, Pingfan Liu wrote: > > MIGRATE_PFN_MIGRATE marks a valid pfn, further more, suitable to migrate. > > As for hole, there is no valid pfn, not to mention migration. > > > > Before this patch, hole has already relied on the following code to be > > filtered out. Hence it is more reasonable to see hole as invalid source > > page. > > migrate_vma_prepare() > > { > > struct page *page = migrate_pfn_to_page(migrate->src[i]); > > > > if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE)) > > \_ this condition > > } > > NAK you break the API, MIGRATE_PFN_MIGRATE is use for 2 things, > first it allow the collection code to mark entry that can be > migrated, then it use by driver to allow driver to skip migration > for some entry (for whatever reason the driver might have), we > still need to keep the entry and not clear it so that we can > cleanup thing (ie remove migration pte entry). Thanks for your kindly review. I read the code again. Maybe I miss something. But as my understanding, for hole, there is no pte. As the current code migrate_vma_collect_pmd() { if (pmd_none(*pmdp)) return migrate_vma_collect_hole(start, end, walk); ... make_migration_entry() } We do not install migration entry for hole, then no need to remove migration pte entry. And on the driver side, there is way to migrate a hole. The driver just skip it by drivers/gpu/drm/nouveau/nouveau_dmem.c: if (!spage || !(src_pfns[i] & MIGRATE_PFN_MIGRATE)) ^^^^ Finally, in migrate_vma_finalize(), for a hole, if (!page) { if (newpage) { unlock_page(newpage); put_page(newpage); } continue; } And we do not rely on remove_migration_ptes(page, newpage, false); to restore the orignal pte (and it is impossible). Thanks, Pingfan