InnoDB Write Log efficiency above 100%
https://dba.stackexchange.com/questions/194832
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10-10-2020 - |
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After running mysqltuner.pl, I get an Innodb write log efficiency way above 100 %. Why? What does it mean?
There is no specific reccomendation from mysqltuner.
DB is MariaDB 10.1.26 on Debian 9.x with 1 GB RAM.
-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 0
[OK] InnoDB File per table is activated
[OK] InnoDB buffer pool / data size: 64.0M/9.0M
[OK] Ratio InnoDB log file size / InnoDB Buffer pool size: 8.0M * 2/64.0M should be equal 25%
[OK] InnoDB buffer pool instances: 1
[--] InnoDB Buffer Pool Chunk Size not used or defined in your version
[OK] InnoDB Read buffer efficiency: 100.00% (116110977 hits/ 116111816 total)
[!!] InnoDB Write Log efficiency: 4857.14% (10880 hits/ 224 total)
[OK] InnoDB log waits: 0.00% (0 waits / 11104 writes)
This is the configuration of InnoDb engine:
innodb ON
innodb-adaptive-flushing TRUE
innodb-adaptive-flushing-lwm 10
innodb-adaptive-hash-index TRUE
innodb-adaptive-hash-index-partitions 1
innodb-adaptive-max-sleep-delay 150000
innodb-additional-mem-pool-size 8388608
innodb-api-bk-commit-interval 5
innodb-api-disable-rowlock FALSE
innodb-api-enable-binlog FALSE
innodb-api-enable-mdl FALSE
innodb-api-trx-level 0
innodb-autoextend-increment 64
innodb-autoinc-lock-mode 1
innodb-background-scrub-data-check-interval 3600
innodb-background-scrub-data-compressed FALSE
innodb-background-scrub-data-interval 604800
innodb-background-scrub-data-uncompressed FALSE
innodb-buf-dump-status-frequency 0
innodb-buffer-page ON
innodb-buffer-page-lru ON
innodb-buffer-pool-dump-at-shutdown FALSE
innodb-buffer-pool-dump-now FALSE
innodb-buffer-pool-dump-pct 100
innodb-buffer-pool-filename ib_buffer_pool
innodb-buffer-pool-instances 1
innodb-buffer-pool-load-abort FALSE
innodb-buffer-pool-load-at-startup FALSE
innodb-buffer-pool-load-now FALSE
innodb-buffer-pool-populate FALSE
innodb-buffer-pool-size 67108864
innodb-buffer-pool-stats ON
innodb-change-buffer-max-size 25
innodb-change-buffering all
innodb-changed-pages ON
innodb-checksum-algorithm INNODB
innodb-checksums TRUE
innodb-cleaner-lsn-age-factor HIGH_CHECKPOINT
innodb-cmp ON
innodb-cmp-per-index ON
innodb-cmp-per-index-enabled FALSE
innodb-cmp-per-index-reset ON
innodb-cmp-reset ON
innodb-cmpmem ON
innodb-cmpmem-reset ON
innodb-commit-concurrency 0
innodb-compression-algorithm zlib
innodb-compression-failure-threshold-pct 5
innodb-compression-level 6
innodb-compression-pad-pct-max 50
innodb-concurrency-tickets 5000
innodb-corrupt-table-action assert
innodb-data-file-path (No default value)
innodb-data-home-dir (No default value)
innodb-default-encryption-key-id 1
innodb-defragment FALSE
innodb-defragment-fill-factor 0.9
innodb-defragment-fill-factor-n-recs 20
innodb-defragment-frequency 40
innodb-defragment-n-pages 7
innodb-defragment-stats-accuracy 0
innodb-disable-sort-file-cache FALSE
innodb-doublewrite TRUE
innodb-empty-free-list-algorithm BACKOFF
innodb-encrypt-log FALSE
innodb-encrypt-tables OFF
innodb-encryption-rotate-key-age 1
innodb-encryption-rotation-iops 100
innodb-encryption-threads 0
innodb-fake-changes FALSE
innodb-fast-shutdown 1
innodb-fatal-semaphore-wait-threshold 600
innodb-file-format Antelope
innodb-file-format-check TRUE
innodb-file-format-max Antelope
innodb-file-io-threads 4
innodb-file-per-table TRUE
innodb-flush-log-at-timeout 1
innodb-flush-log-at-trx-commit 1
innodb-flush-method (No default value)
innodb-flush-neighbors 1
innodb-flushing-avg-loops 30
innodb-force-load-corrupted FALSE
innodb-force-primary-key FALSE
innodb-force-recovery 0
innodb-foreground-preflush EXPONENTIAL_BACKOFF
innodb-ft-aux-table (No default value)
innodb-ft-being-deleted ON
innodb-ft-cache-size 8000000
innodb-ft-config ON
innodb-ft-default-stopword ON
innodb-ft-deleted ON
innodb-ft-enable-diag-print FALSE
innodb-ft-enable-stopword TRUE
innodb-ft-index-cache ON
innodb-ft-index-table ON
innodb-ft-max-token-size 84
innodb-ft-min-token-size 3
innodb-ft-num-word-optimize 2000
innodb-ft-result-cache-limit 2000000000
innodb-ft-server-stopword-table (No default value)
innodb-ft-sort-pll-degree 2
innodb-ft-total-cache-size 640000000
innodb-ft-user-stopword-table (No default value)
innodb-idle-flush-pct 100
innodb-immediate-scrub-data-uncompressed FALSE
innodb-instrument-semaphores FALSE
innodb-io-capacity 200
innodb-io-capacity-max 18446744073709551615
innodb-kill-idle-transaction 0
innodb-large-prefix FALSE
innodb-lock-schedule-algorithm fcfs
innodb-lock-wait-timeout 50
innodb-lock-waits ON
innodb-locking-fake-changes TRUE
innodb-locks ON
innodb-locks-unsafe-for-binlog FALSE
innodb-log-arch-dir (No default value)
innodb-log-arch-expire-sec 0
innodb-log-archive FALSE
innodb-log-block-size 512
innodb-log-buffer-size 16777216
innodb-log-checksum-algorithm INNODB
innodb-log-compressed-pages TRUE
innodb-log-file-size 8388608
innodb-log-files-in-group 2
innodb-log-group-home-dir (No default value)
innodb-lru-scan-depth 1024
innodb-max-bitmap-file-size 104857600
innodb-max-changed-pages 1000000
innodb-max-dirty-pages-pct 75
innodb-max-dirty-pages-pct-lwm 0.001
innodb-max-purge-lag 0
innodb-max-purge-lag-delay 0
innodb-metrics ON
innodb-mirrored-log-groups 0
innodb-monitor-disable (No default value)
innodb-monitor-enable all
innodb-monitor-reset (No default value)
innodb-monitor-reset-all (No default value)
innodb-mtflush-threads 8
innodb-mutexes ON
innodb-old-blocks-pct 37
innodb-old-blocks-time 1000
innodb-online-alter-log-max-size 134217728
innodb-open-files 0
innodb-optimize-fulltext-only FALSE
innodb-page-size 16384
innodb-prefix-index-cluster-optimization FALSE
innodb-print-all-deadlocks FALSE
innodb-purge-batch-size 300
innodb-purge-threads 1
innodb-random-read-ahead FALSE
innodb-read-ahead-threshold 56
innodb-read-io-threads 4
innodb-read-only FALSE
innodb-replication-delay 0
innodb-rollback-on-timeout FALSE
innodb-rollback-segments 128
innodb-sched-priority-cleaner 19
innodb-scrub-log FALSE
innodb-scrub-log-speed 256
innodb-show-locks-held 10
innodb-show-verbose-locks 0
innodb-simulate-comp-failures 0
innodb-sort-buffer-size 1048576
innodb-spin-wait-delay 6
innodb-stats-auto-recalc TRUE
innodb-stats-include-delete-marked FALSE
innodb-stats-method nulls_equal
innodb-stats-modified-counter 0
innodb-stats-on-metadata FALSE
innodb-stats-persistent TRUE
innodb-stats-persistent-sample-pages 20
innodb-stats-sample-pages 8
innodb-stats-traditional TRUE
innodb-stats-transient-sample-pages 8
innodb-status-file FALSE
innodb-status-output FALSE
innodb-status-output-locks FALSE
innodb-strict-mode TRUE
innodb-support-xa TRUE
innodb-sync-array-size 1
innodb-sync-spin-loops 30
innodb-sys-columns ON
innodb-sys-datafiles ON
innodb-sys-fields ON
innodb-sys-foreign ON
innodb-sys-foreign-cols ON
innodb-sys-indexes ON
innodb-sys-semaphore-waits ON
innodb-sys-tables ON
innodb-sys-tablespaces ON
innodb-sys-tablestats ON
innodb-table-locks TRUE
innodb-tablespaces-encryption ON
innodb-tablespaces-scrubbing ON
innodb-thread-concurrency 0
innodb-thread-sleep-delay 10000
innodb-tmpdir (No default value)
innodb-track-changed-pages FALSE
innodb-trx ON
innodb-undo-directory .
innodb-undo-logs 128
innodb-undo-tablespaces 0
innodb-use-atomic-writes FALSE
innodb-use-fallocate FALSE
innodb-use-global-flush-log-at-trx-commit TRUE
innodb-use-mtflush FALSE
innodb-use-native-aio TRUE
innodb-use-stacktrace FALSE
innodb-use-sys-malloc TRUE
innodb-use-trim FALSE
innodb-write-io-threads 4
해결책
That seems to be computed from
abs(Innodb_log_write_requests - Innodb_log_writes) hits /
Innodb_log_write_requests total
where the values come from SHOW GLOBAL STATUS.
"..._write_requests" are when InnoDB needs to write something to iblog on disk. However, writes are buffered in the buffer_pool in hopes of collecting multiple things together a single write once ("..._writes").
Normally multiple "requests" would eventually result in a single "write".
The "abs()" is to hide negative numbers (more writes than requests). Those don't make sense, but do seem to happen.
In the hundred servers I checked, none got more than 100%.
I would ignore the metric -- mysqltuner has issues, and InnoDB seems to be doing something extra with the number to make them less then useful for comparing in this way.
It's hard to get into any performance problems (that tuning can fix) when you have only 9MB of data+index.
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