1

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

1

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

4
  • Thanks for the answer but I am not looking to reduce the workload I want to give it more power (CPU) as RAM is way more of an issue than CPU on our machines – Harmonytalk May 26 at 19:25
  • Well, you can simply increase KSM_NPAGES_MAX and lower KSM_SLEEP_MSEC then. But considering that sharing seems to not increase much, it probably means wasting additional CPU cycles. – shodanshok May 27 at 6:20
  • But the problem is I don't think KSM uses multi threads I can't get it above 100% CPU (SS above) – Harmonytalk May 27 at 9:48
  • Also running KSM_NPAGES_MAX=6000 KSM_SLEEP_MSEC=50 reduced KSM sharing to just 34GB vs 170GB (default settings) with the 100% CPU usage. – Harmonytalk May 27 at 11:07

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