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8578e0c00d
Introduce basic swap table infrastructures, which are now just a fixed-sized flat array inside each swap cluster, with access wrappers. Each cluster contains a swap table of 512 entries. Each table entry is an opaque atomic long. It could be in 3 types: a shadow type (XA_VALUE), a folio type (pointer), or NULL. In this first step, it only supports storing a folio or shadow, and it is a drop-in replacement for the current swap cache. Convert all swap cache users to use the new sets of APIs. Chris Li has been suggesting using a new infrastructure for swap cache for better performance, and that idea combined well with the swap table as the new backing structure. Now the lock contention range is reduced to 2M clusters, which is much smaller than the 64M address_space. And we can also drop the multiple address_space design. All the internal works are done with swap_cache_get_* helpers. Swap cache lookup is still lock-less like before, and the helper's contexts are same with original swap cache helpers. They still require a pin on the swap device to prevent the backing data from being freed. Swap cache updates are now protected by the swap cluster lock instead of the XArray lock. This is mostly handled internally, but new __swap_cache_* helpers require the caller to lock the cluster. So, a few new cluster access and locking helpers are also introduced. A fully cluster-based unified swap table can be implemented on top of this to take care of all count tracking and synchronization work, with dynamic allocation. It should reduce the memory usage while making the performance even better. Link: https://lkml.kernel.org/r/20250916160100.31545-12-ryncsn@gmail.com Co-developed-by: Chris Li <chrisl@kernel.org> Signed-off-by: Chris Li <chrisl@kernel.org> Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Suggested-by: Chris Li <chrisl@kernel.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: kernel test robot <oliver.sang@intel.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Cc: SeongJae Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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