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To: Zi Yan , David Hildenbrand , linux-mm@kvack.org References: <20211209230414.2766515-1-zi.yan@sent.com> From: Eric Ren In-Reply-To: <20211209230414.2766515-1-zi.yan@sent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Mon, 13 Dec 2021 09:47:48 +1100 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: Mel Gorman , Robin Murphy , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Christoph Hellwig , Vlastimil Babka , Marek Szyprowski Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Zi Yan, On 2021/12/10 07:04, Zi Yan wrote: > From: Zi Yan > > Hi all, > > This patchset tries to remove the MAX_ORDER - 1 alignment requirement for CMA > and alloc_contig_range(). It prepares for my upcoming changes to make MAX_ORDER > adjustable at boot time[1]. > > The MAX_ORDER - 1 alignment requirement comes from that alloc_contig_range() > isolates pageblocks to remove free memory from buddy allocator but isolating > only a subset of pageblocks within a page spanning across multiple pageblocks > causes free page accounting issues. Isolated page might not be put into the > right free list, since the code assumes the migratetype of the first pageblock > as the whole free page migratetype. This is based on the discussion at [2]. > > To remove the requirement, this patchset: > 1. still isolates pageblocks at MAX_ORDER - 1 granularity; Then, unplug fails if either pageblock of the  MAX_ORDER - 1 page has unmovable page, right? Thanks, Eric > 2. but saves the pageblock migratetypes outside the specified range of > alloc_contig_range() and restores them after all pages within the range > become free after __alloc_contig_migrate_range(); > 3. splits free pages spanning multiple pageblocks at the beginning and the end > of the range and puts the split pages to the right migratetype free lists > based on the pageblock migratetypes; > 4. returns pages not in the range as it did before this patch. > > Isolation needs to happen at MAX_ORDER - 1 granularity, because otherwise > 1) extra code is needed to detect pages (free, PageHuge, THP, or PageCompound) > to make sure all pageblocks belonging to a single page are isolated together > and later pageblocks outside the range need to have their migratetypes restored; > or 2) extra logic will need to be added during page free time to split a free > page with multi-migratetype pageblocks. > > Two optimizations might come later: > 1. only check unmovable pages within the range instead of MAX_ORDER - 1 aligned > range during isolation to increase successful rate of alloc_contig_range(). > 2. make MIGRATE_ISOLATE a separate bit to avoid saving and restoring existing > migratetypes before and after isolation respectively. > > Feel free to give comments and suggestions. Thanks. > > > [1] https://lore.kernel.org/linux-mm/20210805190253.2795604-1-zi.yan@sent.com/ > [2] https://lore.kernel.org/linux-mm/d19fb078-cb9b-f60f-e310-fdeea1b947d2@redhat.com/ > > > Zi Yan (7): > mm: page_alloc: avoid merging non-fallbackable pageblocks with others. > mm: compaction: handle non-lru compound pages properly in > isolate_migratepages_block(). > mm: migrate: allocate the right size of non hugetlb or THP compound > pages. > mm: make alloc_contig_range work at pageblock granularity > mm: cma: use pageblock_order as the single alignment > drivers: virtio_mem: use pageblock size as the minimum virtio_mem > size. > arch: powerpc: adjust fadump alignment to be pageblock aligned. > > arch/powerpc/include/asm/fadump-internal.h | 4 +- > drivers/virtio/virtio_mem.c | 6 +- > include/linux/mmzone.h | 11 +- > kernel/dma/contiguous.c | 2 +- > mm/cma.c | 6 +- > mm/compaction.c | 10 +- > mm/migrate.c | 8 +- > mm/page_alloc.c | 203 +++++++++++++++++---- > 8 files changed, 196 insertions(+), 54 deletions(-) >