How can I optimize ksm for my machine - 100% CPU usage and limited KSM Sharing (Proxmox)
Proxmox Node Stats
KSM is constantly at 100% CPU usage which makes me believe I need to optimize the /etc/ksmtuned.conf configuration but I am not exactly sure what to set it as for this machine. As you can see from the screenshot above KSM Sharing is currently at 170GB and doesn't seem to want to go any higher than that. I have created test virtual machines, used 100% of the RAM and then stopped the test program and Proxmox RAM usage doesn't return until I turn the virtual machine off. ksmd 100% CPU usage How can I optimize the configuration and if need be allow ksmd to use up to 500% of CPU power (5 CPU)
watch cat /sys/kernel/mm/ksm/pages_sharing - Returns (and doesn't ever go much higher)
44698138
/etc/ksmtuned.conf - Contains
# Configuration file for ksmtuned.
# How long ksmtuned should sleep between tuning adjustments
# KSM_MONITOR_INTERVAL=60
# Millisecond sleep between ksm scans for 16Gb server.
# Smaller servers sleep more, bigger sleep less.
# KSM_SLEEP_MSEC=100
KSM_THRES_COEF=70
# KSM_NPAGES_BOOST=300
# KSM_NPAGES_DECAY=-50
# KSM_NPAGES_MIN=64
# KSM_NPAGES_MAX=1250
# KSM_THRES_COEF=20
# KSM_THRES_CONST=2048
# uncomment the following if you want ksmtuned debug info
LOGFILE=/var/log/ksmtuned
DEBUG=1
I am also using ZFS RAID 10
/etc/modprobe.d/zfs.conf - Contains
#Max Ram Used by ZFS - 64GB
options zfs zfs_arc_max=68719476736
#Min Ram Used by ZFS - 20GB
options zfs zfs_arc_min=21474836480
arc_summary - Returns
------------------------------------------------------------------------
ZFS Subsystem Report Wed May 26 13:21:14 2021
Linux 5.4.114-1-pve 2.0.4-pve1
Machine: ns31407416 (x86_64) 2.0.4-pve1
ARC status: HEALTHY
Memory throttle count: 0
ARC size (current): 98.6 % 63.1 GiB
Target size (adaptive): 100.0 % 64.0 GiB
Min size (hard limit): 31.2 % 20.0 GiB
Max size (high water): 3:1 64.0 GiB
Most Frequently Used (MFU) cache size: 19.5 % 11.3 GiB
Most Recently Used (MRU) cache size: 80.5 % 46.6 GiB
Metadata cache size (hard limit): 75.0 % 48.0 GiB
Metadata cache size (current): 14.4 % 6.9 GiB
Dnode cache size (hard limit): 10.0 % 4.8 GiB
Dnode cache size (current): 0.2 % 11.6 MiB
ARC hash breakdown:
Elements max: 16.9M
Elements current: 81.8 % 13.8M
Collisions: 212.2M
Chain max: 7
Chains: 663.6k
ARC misc:
Deleted: 533.3M
Mutex misses: 49.6k
Eviction skips: 21.5k
ARC total accesses (hits + misses): 4.0G
Cache hit ratio: 86.5 % 3.5G
Cache miss ratio: 13.5 % 542.5M
Actual hit ratio (MFU + MRU hits): 86.0 % 3.4G
Data demand efficiency: 53.9 % 1.1G
Data prefetch efficiency: 40.0 % 52.8M
Cache hits by cache type:
Most frequently used (MFU): 80.9 % 2.8G
Most recently used (MRU): 18.6 % 644.4M
Most frequently used (MFU) ghost: 1.4 % 48.6M
Most recently used (MRU) ghost: 0.1 % 4.2M
Cache hits by data type:
Demand data: 17.1 % 593.8M
Demand prefetch data: 0.6 % 21.1M
Demand metadata: 82.2 % 2.8G
Demand prefetch metadata: < 0.1 % 962.6k
Cache misses by data type:
Demand data: 93.8 % 508.6M
Demand prefetch data: 5.8 % 31.7M
Demand metadata: 0.4 % 2.0M
Demand prefetch metadata: < 0.1 % 198.6k
DMU prefetch efficiency: 252.5M
Hit ratio: 9.8 % 24.7M
Miss ratio: 90.2 % 227.8M
L2ARC not detected, skipping section
Solaris Porting Layer (SPL):
spl_hostid 0
spl_hostid_path /etc/hostid
spl_kmem_alloc_max 1048576
spl_kmem_alloc_warn 65536
spl_kmem_cache_kmem_threads 4
spl_kmem_cache_magazine_size 0
spl_kmem_cache_max_size 32
spl_kmem_cache_obj_per_slab 8
spl_kmem_cache_reclaim 0
spl_kmem_cache_slab_limit 16384
spl_max_show_tasks 512
spl_panic_halt 0
spl_schedule_hrtimeout_slack_us 0
spl_taskq_kick 0
spl_taskq_thread_bind 0
spl_taskq_thread_dynamic 1
spl_taskq_thread_priority 1
spl_taskq_thread_sequential 4
Tunables:
dbuf_cache_hiwater_pct 10
dbuf_cache_lowater_pct 10
dbuf_cache_max_bytes 18446744073709551615
dbuf_cache_shift 5
dbuf_metadata_cache_max_bytes 18446744073709551615
dbuf_metadata_cache_shift 6
dmu_object_alloc_chunk_shift 7
dmu_prefetch_max 134217728
ignore_hole_birth 1
l2arc_feed_again 1
l2arc_feed_min_ms 200
l2arc_feed_secs 1
l2arc_headroom 2
l2arc_headroom_boost 200
l2arc_meta_percent 33
l2arc_mfuonly 0
l2arc_noprefetch 1
l2arc_norw 0
l2arc_rebuild_blocks_min_l2size 1073741824
l2arc_rebuild_enabled 1
l2arc_trim_ahead 0
l2arc_write_boost 8388608
l2arc_write_max 8388608
metaslab_aliquot 524288
metaslab_bias_enabled 1
metaslab_debug_load 0
metaslab_debug_unload 0
metaslab_df_max_search 16777216
metaslab_df_use_largest_segment 0
metaslab_force_ganging 16777217
metaslab_fragmentation_factor_enabled 1
metaslab_lba_weighting_enabled 1
metaslab_preload_enabled 1
metaslab_unload_delay 32
metaslab_unload_delay_ms 600000
send_holes_without_birth_time 1
spa_asize_inflation 24
spa_config_path /etc/zfs/zpool.cache
spa_load_print_vdev_tree 0
spa_load_verify_data 1
spa_load_verify_metadata 1
spa_load_verify_shift 4
spa_slop_shift 5
vdev_file_logical_ashift 9
vdev_file_physical_ashift 9
vdev_removal_max_span 32768
vdev_validate_skip 0
zap_iterate_prefetch 1
zfetch_array_rd_sz 1048576
zfetch_max_distance 8388608
zfetch_max_idistance 67108864
zfetch_max_streams 8
zfetch_min_sec_reap 2
zfs_abd_scatter_enabled 1
zfs_abd_scatter_max_order 10
zfs_abd_scatter_min_size 1536
zfs_admin_snapshot 0
zfs_allow_redacted_dataset_mount 0
zfs_arc_average_blocksize 8192
zfs_arc_dnode_limit 0
zfs_arc_dnode_limit_percent 10
zfs_arc_dnode_reduce_percent 10
zfs_arc_evict_batch_limit 10
zfs_arc_eviction_pct 200
zfs_arc_grow_retry 0
zfs_arc_lotsfree_percent 10
zfs_arc_max 68719476736
zfs_arc_meta_adjust_restarts 4096
zfs_arc_meta_limit 0
zfs_arc_meta_limit_percent 75
zfs_arc_meta_min 0
zfs_arc_meta_prune 10000
zfs_arc_meta_strategy 1
zfs_arc_min 21474836480
zfs_arc_min_prefetch_ms 0
zfs_arc_min_prescient_prefetch_ms 0
zfs_arc_p_dampener_disable 1
zfs_arc_p_min_shift 0
zfs_arc_pc_percent 0
zfs_arc_shrink_shift 0
zfs_arc_shrinker_limit 10000
zfs_arc_sys_free 0
zfs_async_block_max_blocks 18446744073709551615
zfs_autoimport_disable 1
zfs_checksum_events_per_second 20
zfs_commit_timeout_pct 5
zfs_compressed_arc_enabled 1
zfs_condense_indirect_commit_entry_delay_ms 0
zfs_condense_indirect_vdevs_enable 1
zfs_condense_max_obsolete_bytes 1073741824
zfs_condense_min_mapping_bytes 131072
zfs_dbgmsg_enable 1
zfs_dbgmsg_maxsize 4194304
zfs_dbuf_state_index 0
zfs_ddt_data_is_special 1
zfs_deadman_checktime_ms 60000
zfs_deadman_enabled 1
zfs_deadman_failmode wait
zfs_deadman_synctime_ms 600000
zfs_deadman_ziotime_ms 300000
zfs_dedup_prefetch 0
zfs_delay_min_dirty_percent 60
zfs_delay_scale 500000
zfs_delete_blocks 20480
zfs_dirty_data_max 4294967296
zfs_dirty_data_max_max 4294967296
zfs_dirty_data_max_max_percent 25
zfs_dirty_data_max_percent 10
zfs_dirty_data_sync_percent 20
zfs_disable_ivset_guid_check 0
zfs_dmu_offset_next_sync 0
zfs_expire_snapshot 300
zfs_fallocate_reserve_percent 110
zfs_flags 0
zfs_free_bpobj_enabled 1
zfs_free_leak_on_eio 0
zfs_free_min_time_ms 1000
zfs_history_output_max 1048576
zfs_immediate_write_sz 32768
zfs_initialize_chunk_size 1048576
zfs_initialize_value 16045690984833335022
zfs_keep_log_spacemaps_at_export 0
zfs_key_max_salt_uses 400000000
zfs_livelist_condense_new_alloc 0
zfs_livelist_condense_sync_cancel 0
zfs_livelist_condense_sync_pause 0
zfs_livelist_condense_zthr_cancel 0
zfs_livelist_condense_zthr_pause 0
zfs_livelist_max_entries 500000
zfs_livelist_min_percent_shared 75
zfs_lua_max_instrlimit 100000000
zfs_lua_max_memlimit 104857600
zfs_max_async_dedup_frees 100000
zfs_max_log_walking 5
zfs_max_logsm_summary_length 10
zfs_max_missing_tvds 0
zfs_max_nvlist_src_size 0
zfs_max_recordsize 1048576
zfs_metaslab_fragmentation_threshold 70
zfs_metaslab_max_size_cache_sec 3600
zfs_metaslab_mem_limit 75
zfs_metaslab_segment_weight_enabled 1
zfs_metaslab_switch_threshold 2
zfs_mg_fragmentation_threshold 95
zfs_mg_noalloc_threshold 0
zfs_min_metaslabs_to_flush 1
zfs_multihost_fail_intervals 10
zfs_multihost_history 0
zfs_multihost_import_intervals 20
zfs_multihost_interval 1000
zfs_multilist_num_sublists 0
zfs_no_scrub_io 0
zfs_no_scrub_prefetch 0
zfs_nocacheflush 0
zfs_nopwrite_enabled 1
zfs_object_mutex_size 64
zfs_obsolete_min_time_ms 500
zfs_override_estimate_recordsize 0
zfs_pd_bytes_max 52428800
zfs_per_txg_dirty_frees_percent 5
zfs_prefetch_disable 0
zfs_read_history 0
zfs_read_history_hits 0
zfs_rebuild_max_segment 1048576
zfs_reconstruct_indirect_combinations_max 4096
zfs_recover 0
zfs_recv_queue_ff 20
zfs_recv_queue_length 16777216
zfs_recv_write_batch_size 1048576
zfs_removal_ignore_errors 0
zfs_removal_suspend_progress 0
zfs_remove_max_segment 16777216
zfs_resilver_disable_defer 0
zfs_resilver_min_time_ms 3000
zfs_scan_checkpoint_intval 7200
zfs_scan_fill_weight 3
zfs_scan_ignore_errors 0
zfs_scan_issue_strategy 0
zfs_scan_legacy 0
zfs_scan_max_ext_gap 2097152
zfs_scan_mem_lim_fact 20
zfs_scan_mem_lim_soft_fact 20
zfs_scan_strict_mem_lim 0
zfs_scan_suspend_progress 0
zfs_scan_vdev_limit 4194304
zfs_scrub_min_time_ms 1000
zfs_send_corrupt_data 0
zfs_send_no_prefetch_queue_ff 20
zfs_send_no_prefetch_queue_length 1048576
zfs_send_queue_ff 20
zfs_send_queue_length 16777216
zfs_send_unmodified_spill_blocks 1
zfs_slow_io_events_per_second 20
zfs_spa_discard_memory_limit 16777216
zfs_special_class_metadata_reserve_pct 25
zfs_sync_pass_deferred_free 2
zfs_sync_pass_dont_compress 8
zfs_sync_pass_rewrite 2
zfs_sync_taskq_batch_pct 75
zfs_trim_extent_bytes_max 134217728
zfs_trim_extent_bytes_min 32768
zfs_trim_metaslab_skip 0
zfs_trim_queue_limit 10
zfs_trim_txg_batch 32
zfs_txg_history 100
zfs_txg_timeout 5
zfs_unflushed_log_block_max 262144
zfs_unflushed_log_block_min 1000
zfs_unflushed_log_block_pct 400
zfs_unflushed_max_mem_amt 1073741824
zfs_unflushed_max_mem_ppm 1000
zfs_unlink_suspend_progress 0
zfs_user_indirect_is_special 1
zfs_vdev_aggregate_trim 0
zfs_vdev_aggregation_limit 1048576
zfs_vdev_aggregation_limit_non_rotating 131072
zfs_vdev_async_read_max_active 3
zfs_vdev_async_read_min_active 1
zfs_vdev_async_write_active_max_dirty_percent 60
zfs_vdev_async_write_active_min_dirty_percent 30
zfs_vdev_async_write_max_active 10
zfs_vdev_async_write_min_active 2
zfs_vdev_cache_bshift 16
zfs_vdev_cache_max 16384
zfs_vdev_cache_size 0
zfs_vdev_default_ms_count 200
zfs_vdev_default_ms_shift 29
zfs_vdev_initializing_max_active 1
zfs_vdev_initializing_min_active 1
zfs_vdev_max_active 1000
zfs_vdev_max_auto_ashift 16
zfs_vdev_min_auto_ashift 9
zfs_vdev_min_ms_count 16
zfs_vdev_mirror_non_rotating_inc 0
zfs_vdev_mirror_non_rotating_seek_inc 1
zfs_vdev_mirror_rotating_inc 0
zfs_vdev_mirror_rotating_seek_inc 5
zfs_vdev_mirror_rotating_seek_offset 1048576
zfs_vdev_ms_count_limit 131072
zfs_vdev_nia_credit 5
zfs_vdev_nia_delay 5
zfs_vdev_queue_depth_pct 1000
zfs_vdev_raidz_impl cycle [fastest] original scalar sse2 ssse3 avx2
zfs_vdev_read_gap_limit 32768
zfs_vdev_rebuild_max_active 3
zfs_vdev_rebuild_min_active 1
zfs_vdev_removal_max_active 2
zfs_vdev_removal_min_active 1
zfs_vdev_scheduler unused
zfs_vdev_scrub_max_active 3
zfs_vdev_scrub_min_active 1
zfs_vdev_sync_read_max_active 10
zfs_vdev_sync_read_min_active 10
zfs_vdev_sync_write_max_active 10
zfs_vdev_sync_write_min_active 10
zfs_vdev_trim_max_active 2
zfs_vdev_trim_min_active 1
zfs_vdev_write_gap_limit 4096
zfs_vnops_read_chunk_size 1048576
zfs_zevent_cols 80
zfs_zevent_console 0
zfs_zevent_len_max 1536
zfs_zevent_retain_expire_secs 900
zfs_zevent_retain_max 2000
zfs_zil_clean_taskq_maxalloc 1048576
zfs_zil_clean_taskq_minalloc 1024
zfs_zil_clean_taskq_nthr_pct 100
zil_maxblocksize 131072
zil_nocacheflush 0
zil_replay_disable 0
zil_slog_bulk 786432
zio_deadman_log_all 0
zio_dva_throttle_enabled 1
zio_requeue_io_start_cut_in_line 1
zio_slow_io_ms 30000
zio_taskq_batch_pct 75
zvol_inhibit_dev 0
zvol_major 230
zvol_max_discard_blocks 16384
zvol_prefetch_bytes 131072
zvol_request_sync 0
zvol_threads 32
zvol_volmode 1
VDEV cache disabled, skipping section
ZIL committed transactions: 294.4M
Commit requests: 162.6M
Flushes to stable storage: 162.6M
Transactions to SLOG storage pool: 0 Bytes 0
Transactions to non-SLOG storage pool: 8.8 TiB 227.3M
/var/log/ksmtuned - https://pastebin.com/HmDJTyTu
To limit ksmd impact, you can increase KSM_SLEEP_MSEC or, probably better, limit the amount of pages scanned per iteration by reducing KSM_NPAGES_MAX.
So a quick fix would be to set KSM_NPAGES_MAX=300
Moreover, your KSM_THRES_COEF is way too high - you are scanning even with ample free RAM. Consider reverting it to 20
EDIT: if you want to increase CPU load by ksmd, you can simply do the inverse, increasing KSM_NPAGES_MAX and decreasing KSM_SLEEP_MSEC