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 F1BDCC433EF for ; Wed, 2 Feb 2022 12:19:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344085AbiBBMTD (ORCPT ); Wed, 2 Feb 2022 07:19:03 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:51044 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238493AbiBBMS6 (ORCPT ); Wed, 2 Feb 2022 07:18:58 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id AF82C210F6; Wed, 2 Feb 2022 12:18:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1643804337; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=dyPSpPed0+9M2XwlKQxCWeOGFdixxutcj0lTKCCpUgE=; b=u76Vu7FI2iLzLD3FOVgP2Vix8282DDpGEUlqFJuJoAb7GsoqZiiQsX/AprPIwhS/GWi56p hD+5Ugm1z+vcC2tF3t7VCAeaDd4J+dj0QTX3rdLFl2N7ndUKlhA7S+LDyQ54YGDmYJubxZ g1MR8ScpZe9y57RPNVrdPTNnYe+HjjY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1643804337; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=dyPSpPed0+9M2XwlKQxCWeOGFdixxutcj0lTKCCpUgE=; b=s2082Jsn9mldjm1PkVxfSrWcQSpPxDldSrSOzFSMI7rwrn/600G2/luQBlMLKmomZx067+ PsS1l+MmKwK7JVAA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 4142913E18; Wed, 2 Feb 2022 12:18:56 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 4KsvDLB2+mElIgAAMHmgww (envelope-from ); Wed, 02 Feb 2022 12:18:56 +0000 Date: Wed, 2 Feb 2022 13:18:54 +0100 From: Oscar Salvador To: Zi Yan Cc: David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michael Ellerman , Christoph Hellwig , Marek Szyprowski , Robin Murphy , linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, Vlastimil Babka , Mel Gorman , Eric Ren Subject: Re: [PATCH v4 3/7] mm: page_isolation: check specified range for unmovable pages Message-ID: References: <20220119190623.1029355-1-zi.yan@sent.com> <20220119190623.1029355-4-zi.yan@sent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220119190623.1029355-4-zi.yan@sent.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 19, 2022 at 02:06:19PM -0500, Zi Yan wrote: > From: Zi Yan > > Enable set_migratetype_isolate() to check specified sub-range for > unmovable pages during isolation. Page isolation is done > at max(MAX_ORDER_NR_PAEGS, pageblock_nr_pages) granularity, but not all > pages within that granularity are intended to be isolated. For example, > alloc_contig_range(), which uses page isolation, allows ranges without > alignment. This commit makes unmovable page check only look for > interesting pages, so that page isolation can succeed for any > non-overlapping ranges. Another thing that came to my mind. Prior to this patch, has_unmovable_pages() was checking on pageblock granularity, starting at pfn#0 of the pageblock. With this patch, you no longer check on pageblock granularity, which means you might isolate a pageblock, but some pages that sneaked in might actually be unmovable. E.g: Let's say you have a pageblock that spans (pfn#512,pfn#1024), and you pass alloc_contig_range() (pfn#514,pfn#1024). has_unmovable_pages() will start checking the pageblock at pfn#514, and so it will mis pfn#512 and pfn#513. Isn't that a problem, if those pfn turn out to be actually unmovable? -- Oscar Salvador SUSE Labs