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 91ADAC433EF for ; Tue, 30 Nov 2021 10:08:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240676AbhK3KMQ (ORCPT ); Tue, 30 Nov 2021 05:12:16 -0500 Received: from outbound-smtp38.blacknight.com ([46.22.139.221]:39467 "EHLO outbound-smtp38.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240550AbhK3KMP (ORCPT ); Tue, 30 Nov 2021 05:12:15 -0500 Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp38.blacknight.com (Postfix) with ESMTPS id 9B3181E40 for ; Tue, 30 Nov 2021 10:08:55 +0000 (GMT) Received: (qmail 25169 invoked from network); 30 Nov 2021 10:08:55 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 30 Nov 2021 10:08:55 -0000 Date: Tue, 30 Nov 2021 10:08:53 +0000 From: Mel Gorman To: Vlastimil Babka Cc: Zi Yan , 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 Subject: Re: [RFC PATCH 0/3] Use pageblock_order for cma and alloc_contig_range alignment. Message-ID: <20211130100853.GP3366@techsingularity.net> References: <20211115193725.737539-1-zi.yan@sent.com> <3083463d-978b-fbe6-dadf-670d400ed437@suse.cz> <52dbf824-76be-cc34-3983-d45510b1b618@suse.cz> <35A20739-152A-450E-8535-2236D2B28748@nvidia.com> <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 30, 2021 at 10:11:36AM +0100, Vlastimil Babka wrote: > >>> I find that two pageblocks with different migratetypes, like MIGRATE_RECLAIMABLE > >>> and MIGRATE_MOVABLE can be merged into a single free page after I checked > >>> __free_one_page() in detail and printed pageblock information during buddy page > >>> merging. > >> > >> Yes, that can happen. > >> > >> I am not sure what consequence it will cause. Do you have any idea? > >> > >> For MIGRATE_RECLAIMABLE or MIGRATE_MOVABLE or even MIGRATE_UNMOVABLE it's > >> absolutely fine. As long as these pageblocks are fully free (and they are if > >> it's a single free page spanning 2 pageblocks), they can be of any of these > >> type, as they can be reused as needed without causing fragmentation. > >> > >> But in case of MIGRATE_CMA and MIGRATE_ISOLATE, uncontrolled merging would > >> break the specifics of those types. That's why the code is careful for > >> MIGRATE_ISOLATE, and MIGRATE_CMA was until now done in MAX_ORDER granularity. > > > > Thanks for the explanation. Basically migratetypes that can fall back to each > > other can be merged into a single free page, right? > > Yes. > > > How about MIGRATE_HIGHATOMIC? It should not be merged with other migratetypes > > from my understanding. > > Hmm it shouldn't minimally because it has an accounting that would become > broken. So it should prevent merging or make sure the reservations are with > MAX_ORDER granularity, but seems that neither is true? CCing Mel. > MIGRATE_HIGHATOMIC pageblocks can have pages allocated of different types, particularly UNMOVABLE and potentially RECLAIMABLE. The reserving or releasing MIGRATE_HIGHATOMIC pageblocks should be done with reserve_highatomic_pageblock and unreserve_highatomic_pageblock to get the accounting right. However, there does not appear to be any special protection against a page in a highatomic pageblock getting merged with a buddy of another pageblock type. The pageblock would still have the right setting but on allocation, the pages could split to the wrong free list and be lost until the pages belonging to MIGRATE_HIGHATOMIC were freed again. Not sure how much of a problem that is in practice, it's been a while since I've heard of high-order atomic allocation failures. -- Mel Gorman SUSE Labs 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0C6CDC433F5 for ; Tue, 30 Nov 2021 10:16:05 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4J3J5c2vkSz3c9K for ; Tue, 30 Nov 2021 21:16:04 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=techsingularity.net (client-ip=46.22.139.233; helo=outbound-smtp16.blacknight.com; envelope-from=mgorman@techsingularity.net; receiver=) X-Greylist: delayed 395 seconds by postgrey-1.36 at boromir; Tue, 30 Nov 2021 21:15:37 AEDT Received: from outbound-smtp16.blacknight.com (outbound-smtp16.blacknight.com [46.22.139.233]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4J3J556W8Vz300S for ; Tue, 30 Nov 2021 21:15:37 +1100 (AEDT) Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp16.blacknight.com (Postfix) with ESMTPS id A58001C408B for ; Tue, 30 Nov 2021 10:08:55 +0000 (GMT) Received: (qmail 25169 invoked from network); 30 Nov 2021 10:08:55 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 30 Nov 2021 10:08:55 -0000 Date: Tue, 30 Nov 2021 10:08:53 +0000 From: Mel Gorman To: Vlastimil Babka Subject: Re: [RFC PATCH 0/3] Use pageblock_order for cma and alloc_contig_range alignment. Message-ID: <20211130100853.GP3366@techsingularity.net> References: <20211115193725.737539-1-zi.yan@sent.com> <3083463d-978b-fbe6-dadf-670d400ed437@suse.cz> <52dbf824-76be-cc34-3983-d45510b1b618@suse.cz> <35A20739-152A-450E-8535-2236D2B28748@nvidia.com> <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Hildenbrand , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Zi Yan , Robin Murphy , Christoph Hellwig , Marek Szyprowski Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Nov 30, 2021 at 10:11:36AM +0100, Vlastimil Babka wrote: > >>> I find that two pageblocks with different migratetypes, like MIGRATE_RECLAIMABLE > >>> and MIGRATE_MOVABLE can be merged into a single free page after I checked > >>> __free_one_page() in detail and printed pageblock information during buddy page > >>> merging. > >> > >> Yes, that can happen. > >> > >> I am not sure what consequence it will cause. Do you have any idea? > >> > >> For MIGRATE_RECLAIMABLE or MIGRATE_MOVABLE or even MIGRATE_UNMOVABLE it's > >> absolutely fine. As long as these pageblocks are fully free (and they are if > >> it's a single free page spanning 2 pageblocks), they can be of any of these > >> type, as they can be reused as needed without causing fragmentation. > >> > >> But in case of MIGRATE_CMA and MIGRATE_ISOLATE, uncontrolled merging would > >> break the specifics of those types. That's why the code is careful for > >> MIGRATE_ISOLATE, and MIGRATE_CMA was until now done in MAX_ORDER granularity. > > > > Thanks for the explanation. Basically migratetypes that can fall back to each > > other can be merged into a single free page, right? > > Yes. > > > How about MIGRATE_HIGHATOMIC? It should not be merged with other migratetypes > > from my understanding. > > Hmm it shouldn't minimally because it has an accounting that would become > broken. So it should prevent merging or make sure the reservations are with > MAX_ORDER granularity, but seems that neither is true? CCing Mel. > MIGRATE_HIGHATOMIC pageblocks can have pages allocated of different types, particularly UNMOVABLE and potentially RECLAIMABLE. The reserving or releasing MIGRATE_HIGHATOMIC pageblocks should be done with reserve_highatomic_pageblock and unreserve_highatomic_pageblock to get the accounting right. However, there does not appear to be any special protection against a page in a highatomic pageblock getting merged with a buddy of another pageblock type. The pageblock would still have the right setting but on allocation, the pages could split to the wrong free list and be lost until the pages belonging to MIGRATE_HIGHATOMIC were freed again. Not sure how much of a problem that is in practice, it's been a while since I've heard of high-order atomic allocation failures. -- Mel Gorman SUSE Labs 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 smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6A1B9C433EF for ; Tue, 30 Nov 2021 10:16:07 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 1AD2B40475; Tue, 30 Nov 2021 10:16:07 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id HJea2GPe7oZU; Tue, 30 Nov 2021 10:16:06 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp4.osuosl.org (Postfix) with ESMTPS id D6D9D40465; Tue, 30 Nov 2021 10:16:05 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id B309CC0012; Tue, 30 Nov 2021 10:16:05 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 8373FC000A for ; Tue, 30 Nov 2021 10:16:04 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 61FFF81769 for ; Tue, 30 Nov 2021 10:16:04 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KsnEIpp9Hg-3 for ; Tue, 30 Nov 2021 10:16:03 +0000 (UTC) X-Greylist: delayed 00:07:05 by SQLgrey-1.8.0 Received: from outbound-smtp48.blacknight.com (outbound-smtp48.blacknight.com [46.22.136.219]) by smtp1.osuosl.org (Postfix) with ESMTPS id B084681768 for ; Tue, 30 Nov 2021 10:16:03 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp48.blacknight.com (Postfix) with ESMTPS id A9726FAF40 for ; Tue, 30 Nov 2021 10:08:55 +0000 (GMT) Received: (qmail 25169 invoked from network); 30 Nov 2021 10:08:55 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 30 Nov 2021 10:08:55 -0000 Date: Tue, 30 Nov 2021 10:08:53 +0000 From: Mel Gorman To: Vlastimil Babka Subject: Re: [RFC PATCH 0/3] Use pageblock_order for cma and alloc_contig_range alignment. Message-ID: <20211130100853.GP3366@techsingularity.net> References: <20211115193725.737539-1-zi.yan@sent.com> <3083463d-978b-fbe6-dadf-670d400ed437@suse.cz> <52dbf824-76be-cc34-3983-d45510b1b618@suse.cz> <35A20739-152A-450E-8535-2236D2B28748@nvidia.com> <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: David Hildenbrand , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Zi Yan , Robin Murphy , Christoph Hellwig X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Tue, Nov 30, 2021 at 10:11:36AM +0100, Vlastimil Babka wrote: > >>> I find that two pageblocks with different migratetypes, like MIGRATE_RECLAIMABLE > >>> and MIGRATE_MOVABLE can be merged into a single free page after I checked > >>> __free_one_page() in detail and printed pageblock information during buddy page > >>> merging. > >> > >> Yes, that can happen. > >> > >> I am not sure what consequence it will cause. Do you have any idea? > >> > >> For MIGRATE_RECLAIMABLE or MIGRATE_MOVABLE or even MIGRATE_UNMOVABLE it's > >> absolutely fine. As long as these pageblocks are fully free (and they are if > >> it's a single free page spanning 2 pageblocks), they can be of any of these > >> type, as they can be reused as needed without causing fragmentation. > >> > >> But in case of MIGRATE_CMA and MIGRATE_ISOLATE, uncontrolled merging would > >> break the specifics of those types. That's why the code is careful for > >> MIGRATE_ISOLATE, and MIGRATE_CMA was until now done in MAX_ORDER granularity. > > > > Thanks for the explanation. Basically migratetypes that can fall back to each > > other can be merged into a single free page, right? > > Yes. > > > How about MIGRATE_HIGHATOMIC? It should not be merged with other migratetypes > > from my understanding. > > Hmm it shouldn't minimally because it has an accounting that would become > broken. So it should prevent merging or make sure the reservations are with > MAX_ORDER granularity, but seems that neither is true? CCing Mel. > MIGRATE_HIGHATOMIC pageblocks can have pages allocated of different types, particularly UNMOVABLE and potentially RECLAIMABLE. The reserving or releasing MIGRATE_HIGHATOMIC pageblocks should be done with reserve_highatomic_pageblock and unreserve_highatomic_pageblock to get the accounting right. However, there does not appear to be any special protection against a page in a highatomic pageblock getting merged with a buddy of another pageblock type. The pageblock would still have the right setting but on allocation, the pages could split to the wrong free list and be lost until the pages belonging to MIGRATE_HIGHATOMIC were freed again. Not sure how much of a problem that is in practice, it's been a while since I've heard of high-order atomic allocation failures. -- Mel Gorman SUSE Labs _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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 smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 67D0DC433F5 for ; Tue, 30 Nov 2021 10:15:38 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id EE3A340470; Tue, 30 Nov 2021 10:15:37 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tLk4zKlxNxFJ; Tue, 30 Nov 2021 10:15:37 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp4.osuosl.org (Postfix) with ESMTPS id 8412C40465; Tue, 30 Nov 2021 10:15:36 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5BADCC0012; Tue, 30 Nov 2021 10:15:36 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [IPv6:2605:bc80:3010::133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5FCD8C000A for ; Tue, 30 Nov 2021 10:15:34 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 3BCB240114 for ; Tue, 30 Nov 2021 10:15:34 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id bXcRY1qVFhas for ; Tue, 30 Nov 2021 10:15:32 +0000 (UTC) X-Greylist: delayed 00:06:34 by SQLgrey-1.8.0 Received: from outbound-smtp38.blacknight.com (outbound-smtp38.blacknight.com [46.22.139.221]) by smtp2.osuosl.org (Postfix) with ESMTPS id 970AA40018 for ; Tue, 30 Nov 2021 10:15:32 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp38.blacknight.com (Postfix) with ESMTPS id A7AA21E48 for ; Tue, 30 Nov 2021 10:08:55 +0000 (GMT) Received: (qmail 25169 invoked from network); 30 Nov 2021 10:08:55 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 30 Nov 2021 10:08:55 -0000 Date: Tue, 30 Nov 2021 10:08:53 +0000 From: Mel Gorman To: Vlastimil Babka Subject: Re: [RFC PATCH 0/3] Use pageblock_order for cma and alloc_contig_range alignment. Message-ID: <20211130100853.GP3366@techsingularity.net> References: <20211115193725.737539-1-zi.yan@sent.com> <3083463d-978b-fbe6-dadf-670d400ed437@suse.cz> <52dbf824-76be-cc34-3983-d45510b1b618@suse.cz> <35A20739-152A-450E-8535-2236D2B28748@nvidia.com> <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1c67bb96-24db-f5a6-7520-3d97e54e5192@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Zi Yan , Robin Murphy , Christoph Hellwig , Marek Szyprowski X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Tue, Nov 30, 2021 at 10:11:36AM +0100, Vlastimil Babka wrote: > >>> I find that two pageblocks with different migratetypes, like MIGRATE_RECLAIMABLE > >>> and MIGRATE_MOVABLE can be merged into a single free page after I checked > >>> __free_one_page() in detail and printed pageblock information during buddy page > >>> merging. > >> > >> Yes, that can happen. > >> > >> I am not sure what consequence it will cause. Do you have any idea? > >> > >> For MIGRATE_RECLAIMABLE or MIGRATE_MOVABLE or even MIGRATE_UNMOVABLE it's > >> absolutely fine. As long as these pageblocks are fully free (and they are if > >> it's a single free page spanning 2 pageblocks), they can be of any of these > >> type, as they can be reused as needed without causing fragmentation. > >> > >> But in case of MIGRATE_CMA and MIGRATE_ISOLATE, uncontrolled merging would > >> break the specifics of those types. That's why the code is careful for > >> MIGRATE_ISOLATE, and MIGRATE_CMA was until now done in MAX_ORDER granularity. > > > > Thanks for the explanation. Basically migratetypes that can fall back to each > > other can be merged into a single free page, right? > > Yes. > > > How about MIGRATE_HIGHATOMIC? It should not be merged with other migratetypes > > from my understanding. > > Hmm it shouldn't minimally because it has an accounting that would become > broken. So it should prevent merging or make sure the reservations are with > MAX_ORDER granularity, but seems that neither is true? CCing Mel. > MIGRATE_HIGHATOMIC pageblocks can have pages allocated of different types, particularly UNMOVABLE and potentially RECLAIMABLE. The reserving or releasing MIGRATE_HIGHATOMIC pageblocks should be done with reserve_highatomic_pageblock and unreserve_highatomic_pageblock to get the accounting right. However, there does not appear to be any special protection against a page in a highatomic pageblock getting merged with a buddy of another pageblock type. The pageblock would still have the right setting but on allocation, the pages could split to the wrong free list and be lost until the pages belonging to MIGRATE_HIGHATOMIC were freed again. Not sure how much of a problem that is in practice, it's been a while since I've heard of high-order atomic allocation failures. -- Mel Gorman SUSE Labs _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization