Hi, I have found the node_pagecache_reclaimable() function can't calculate reclaimable pages accurately. If reclaim mode doesn't allow UNMAP and WRITE operations, this function will perform the following calculation: reclaimable file pages = total unmapped file pages - vm_stat[NR_FILE_DIRTY] If NR_FILE_DIRTY only counts unmapped dirty pages, the result will be unmapped clean pages. This indeed makes sense. However, I find vm_stat[NR_FILE_DIRTY] also counts some *mapped* dirty pages. If we subtract these mapped pages from unmapped pages, I don't think this is reasonable. This code path can account dirty pages into NR_FILE_DIRTY: account_page_dirtied+0x0/0x2d8 mark_buffer_dirty+0x16c/0x1a0 __block_commit_write.isra.11+0xa8/0xf0 block_write_end+0x58/0xb0 generic_write_end+0x5c/0xc0 ext4_da_write_end+0x128/0x2e8 [ext4] generic_perform_write+0x108/0x1a8 __generic_file_write_iter+0x158/0x1c8 ext4_file_write_iter+0x120/0x3e8 [ext4] __vfs_write+0x11c/0x190 vfs_write+0xac/0x1c0 ksys_write+0x74/0xf0 __arm64_sys_write+0x24/0x30 el0_svc_common+0x78/0x130 el0_svc_handler+0x38/0x78 el0_svc+0x8/0xc Regards, Hao Lee
