Zfs
ZFS：arc_prune 正在使用 100% 的 CPU，平均負載較高
我有一個帶有兩個 ZFS raidz1 池的****4 磁碟儲存伺服器，昨晚它突然開始以100% CPU執行，平均負載很高：
root@stg1:~# w 07:05:48 up 296 days, 17:19, 1 user, load average: 27.06, 25.49, 24.74 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT我有許多正在消耗大量 CPU 的 arc_prune 程序：
我的
zfs_arc_max大小是預設大小（應該是系統 RAM 的 50%），實際上它使用的大小不超過 16 Gb：------------------------------------------------------------------------ ZFS Subsystem Report Thu Aug 27 07:09:34 2020 ARC Summary: (HEALTHY) Memory Throttle Count: 0 ARC Misc: Deleted: 567.62m Mutex Misses: 10.46m Evict Skips: 10.46m ARC Size: 102.63% 15.99 GiB Target Size: (Adaptive) 100.00% 15.58 GiB Min Size (Hard Limit): 6.25% 996.88 MiB Max Size (High Water): 16:1 15.58 GiB ARC Size Breakdown: Recently Used Cache Size: 56.67% 9.06 GiB Frequently Used Cache Size: 43.33% 6.93 GiB ARC Hash Breakdown: Elements Max: 1.48m Elements Current: 21.99% 325.26k Collisions: 62.96m Chain Max: 6 Chains: 12.66k ARC Total accesses: 36.36b Cache Hit Ratio: 81.78% 29.74b Cache Miss Ratio: 18.22% 6.62b Actual Hit Ratio: 81.55% 29.65b Data Demand Efficiency: 89.52% 598.92m Data Prefetch Efficiency: 22.19% 7.58m CACHE HITS BY CACHE LIST: Anonymously Used: 0.18% 53.22m Most Recently Used: 2.05% 608.89m Most Frequently Used: 97.66% 29.04b Most Recently Used Ghost: 0.05% 14.79m Most Frequently Used Ghost: 0.06% 17.72m CACHE HITS BY DATA TYPE: Demand Data: 1.80% 536.16m Prefetch Data: 0.01% 1.68m Demand Metadata: 97.83% 29.09b Prefetch Metadata: 0.36% 107.49m CACHE MISSES BY DATA TYPE: Demand Data: 0.95% 62.77m Prefetch Data: 0.09% 5.89m Demand Metadata: 97.10% 6.43b Prefetch Metadata: 1.87% 123.70m DMU Prefetch Efficiency: 12.04b Hit Ratio: 1.04% 124.91m Miss Ratio: 98.96% 11.92b ZFS Tunable: zfs_arc_p_min_shift 0 zfs_checksums_per_second 20 zvol_request_sync 0 zfs_object_mutex_size 64 spa_slop_shift 5 zfs_sync_taskq_batch_pct 75 zfs_vdev_async_write_max_active 10 zfs_multilist_num_sublists 0 zfs_no_scrub_prefetch 0 zfs_vdev_sync_read_min_active 10 zfs_dmu_offset_next_sync 0 metaslab_debug_load 0 zfs_vdev_mirror_rotating_seek_inc 5 zfs_vdev_mirror_non_rotating_inc 0 zfs_read_history 0 zfs_multihost_history 0 zfs_metaslab_switch_threshold 2 metaslab_fragmentation_factor_enabled 1 zfs_admin_snapshot 1 zfs_delete_blocks 20480 zfs_arc_meta_prune 10000 zfs_free_min_time_ms 1000 zfs_dedup_prefetch 0 zfs_txg_history 0 zfs_vdev_max_active 1000 zfs_vdev_sync_write_min_active 10 spa_load_verify_data 1 zfs_dirty_data_max_max 4294967296 zfs_send_corrupt_data 0 zfs_scan_min_time_ms 1000 dbuf_cache_lowater_pct 10 zfs_send_queue_length 16777216 dmu_object_alloc_chunk_shift 7 zfs_arc_shrink_shift 0 zfs_resilver_min_time_ms 3000 zfs_free_bpobj_enabled 1 zfs_vdev_mirror_non_rotating_seek_inc 1 zfs_vdev_cache_max 16384 ignore_hole_birth 1 zfs_multihost_fail_intervals 5 zfs_arc_sys_free 0 zfs_sync_pass_dont_compress 5 zio_taskq_batch_pct 75 zfs_arc_meta_limit_percent 75 zfs_arc_p_dampener_disable 1 spa_load_verify_metadata 1 dbuf_cache_hiwater_pct 10 zfs_read_chunk_size 1048576 zfs_arc_grow_retry 0 metaslab_aliquot 524288 zfs_vdev_async_read_min_active 1 zfs_vdev_cache_bshift 16 metaslab_preload_enabled 1 l2arc_feed_min_ms 200 zfs_scrub_delay 4 zfs_read_history_hits 0 zfetch_max_distance 8388608 send_holes_without_birth_time 1 zfs_max_recordsize 1048576 zfs_dbuf_state_index 0 dbuf_cache_max_bytes 104857600 zfs_zevent_cols 80 zfs_no_scrub_io 0 zil_slog_bulk 786432 spa_asize_inflation 24 l2arc_write_boost 8388608 zfs_arc_meta_limit 0 zfs_deadman_enabled 1 zfs_abd_scatter_enabled 1 zfs_vdev_async_write_active_min_dirty_percent 30 zfs_free_leak_on_eio 0 zfs_vdev_cache_size 0 zfs_vdev_write_gap_limit 4096 l2arc_headroom 2 zfs_per_txg_dirty_frees_percent 30 zfs_compressed_arc_enabled 1 zfs_scan_ignore_errors 0 zfs_resilver_delay 2 zfs_metaslab_segment_weight_enabled 1 zfs_dirty_data_max_max_percent 25 zio_dva_throttle_enabled 1 zfs_vdev_scrub_min_active 1 zfs_arc_average_blocksize 8192 zfs_vdev_queue_depth_pct 1000 zfs_multihost_interval 1000 zio_requeue_io_start_cut_in_line 1 spa_load_verify_maxinflight 10000 zfetch_max_streams 8 zfs_multihost_import_intervals 10 zfs_mdcomp_disable 0 zfs_zevent_console 0 zfs_sync_pass_deferred_free 2 zfs_nocacheflush 0 zfs_arc_dnode_limit 0 zfs_delays_per_second 20 zfs_dbgmsg_enable 0 zfs_scan_idle 50 zfs_vdev_raidz_impl [fastest] original scalar zio_delay_max 30000 zvol_threads 32 zfs_vdev_async_write_min_active 2 zfs_vdev_sync_read_max_active 10 l2arc_headroom_boost 200 zfs_sync_pass_rewrite 2 spa_config_path /etc/zfs/zpool.cache zfs_pd_bytes_max 52428800 zfs_dirty_data_sync 67108864 zfs_flags 0 zfs_deadman_checktime_ms 5000 zfs_dirty_data_max_percent 10 zfetch_min_sec_reap 2 zfs_mg_noalloc_threshold 0 zfs_arc_meta_min 0 zvol_prefetch_bytes 131072 zfs_deadman_synctime_ms 1000000 zfs_autoimport_disable 1 zfs_arc_min 0 l2arc_noprefetch 1 zfs_nopwrite_enabled 1 l2arc_feed_again 1 zfs_vdev_sync_write_max_active 10 zfs_prefetch_disable 0 zfetch_array_rd_sz 1048576 zfs_metaslab_fragmentation_threshold 70 l2arc_write_max 8388608 zfs_dbgmsg_maxsize 4194304 zfs_vdev_read_gap_limit 32768 zfs_delay_min_dirty_percent 60 zfs_recv_queue_length 16777216 zfs_vdev_async_write_active_max_dirty_percent 60 metaslabs_per_vdev 200 zfs_arc_lotsfree_percent 10 zfs_immediate_write_sz 32768 zil_replay_disable 0 zfs_vdev_mirror_rotating_inc 0 zvol_volmode 1 zfs_arc_meta_strategy 1 dbuf_cache_max_shift 5 metaslab_bias_enabled 1 zfs_vdev_async_read_max_active 3 l2arc_feed_secs 1 zfs_arc_max 0 zfs_zevent_len_max 256 zfs_free_max_blocks 100000 zfs_top_maxinflight 32 zfs_arc_meta_adjust_restarts 4096 l2arc_norw 0 zfs_recover 0 zvol_inhibit_dev 0 zfs_vdev_aggregation_limit 131072 zvol_major 230 metaslab_debug_unload 0 metaslab_lba_weighting_enabled 1 zfs_txg_timeout 5 zfs_arc_min_prefetch_lifespan 0 zfs_vdev_scrub_max_active 2 zfs_vdev_mirror_rotating_seek_offset 1048576 zfs_arc_pc_percent 0 zfs_vdev_scheduler noop zvol_max_discard_blocks 16384 zfs_arc_dnode_reduce_percent 10 zfs_dirty_data_max 3344961536 zfs_abd_scatter_max_order 10 zfs_expire_snapshot 300 zfs_arc_dnode_limit_percent 10 zfs_delay_scale 500000 zfs_mg_fragmentation_threshold 85這些是我的 ZFS 池：
root@stg1:~# zpool status pool: bpool state: ONLINE status: Some supported features are not enabled on the pool. The pool can still be used, but some features are unavailable. action: Enable all features using 'zpool upgrade'. Once this is done, the pool may no longer be accessible by software that does not support the features. See zpool-features(5) for details. scan: scrub repaired 0B in 0h0m with 0 errors on Sun Aug 9 00:24:06 2020 config: NAME STATE READ WRITE CKSUM bpool ONLINE 0 0 0 raidz1-0 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEJRYJ7N-part3 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEKELZTZ-part3 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEKEW7PZ-part3 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEKG492Z-part3 ONLINE 0 0 0 errors: No known data errors pool: rpool state: ONLINE scan: scrub repaired 0B in 7h34m with 0 errors on Sun Aug 9 07:58:40 2020 config: NAME STATE READ WRITE CKSUM rpool ONLINE 0 0 0 raidz1-0 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEJRYJ7N-part4 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEKELZTZ-part4 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEKEW7PZ-part4 ONLINE 0 0 0 ata-HGST_HUH721010ALE600_JEKG492Z-part4 ONLINE 0 0 0 errors: No known data errors驅動器是 SATA，不幸的是我無法添加任何記憶體 SSD 設備。
我能做些什麼來釋放一些 CPU 嗎？
有些東西迫使 ZFS 通過縮小 ARC 來回收記憶體。要立即解決此問題，您可以嘗試發出
echo 1 > /proc/sys/vm/drop_caches僅刪除 Linux 頁面記憶體，或
echo 3 > /proc/sys/vm/drop_caches刪除 Linux 頁面記憶體和ARC但是，為了再次避免它，您應該確定導致記憶體壓力的原因，並在需要時將
zfs_arc_min其設置為zfs_arc_max（基本上禁用 ARC prune）。編輯：根據您的
free輸出，您的問題似乎與頁面記憶體無關。相反，您目前的 ARC 大小大於，zfs_arc_max導致收縮執行緒被喚醒。但是，似乎他們無法釋放任何記憶體。我建議寫信給 zfs 郵件列表zfs-discuss@list.zfsonlinux.org以獲得進一步的幫助。如果您需要立即解決，請發出上述第二條命令 (echo 3 > /proc/sys/vm/drop_caches)