Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Tuning Linux for Databases

Tuning Linux for Databases

Slides from my talk at HDConf 2016 Minsk, Belarus

Alexey Lesovsky

October 15, 2016
Tweet

More Decks by Alexey Lesovsky

Other Decks in Education

Transcript

  1. About PostgreSQL DBA. Linux system administrator. PostgreSQL-Consulting.com: • 24/7 support.

    • Audit, performance optimizations. • Consulting and Training. • Monitoring and Emergency. • Capacity planning. Slides: https://goo.gl/awmZ2H
  2. Agenda RDBMS on Linux, why? Databases and Resources. OS subsystems.

    CPU, Process scheduling, Power saving policies. Memory, VM, NUMA, Huge pages. Storage, File Systems, Input/Output. Other misc.
  3. Why Linux? Linux is a good choice: • Active development

    & Community support. • A lot of features & Fast implementation. • Stable & Mature & Durable.
  4. Databases & Resources Concurrency Query speed Sort, group, hash,... OS

    page cache DB buffer pool Local process cache DB data files Transaction Log Cold start CPU Memory Storage
  5. Databases & Resources CPU Scheduling NUMA Power Saving Virtual Memory

    NUMA Huge Pages File Systems Storage I/O CPU Memory Storage
  6. Resources CPU scheduler. Virtual memory and NUMA. Huge pages. File

    systems. Storage IO. Power saving policy. Others.
  7. CPU scheduling CPU scheduler responsible for proper processes planning: Sysctl:

    • kernel.sched_migration_cost_ns = 5000000 (default: 500000). • kernel.sched_autogroup_enabled = 0 (default: 1). http://www.postgresql.org/message-id/[email protected] http://kernelnewbies.org/Linux_2_6_38#head-59575a6aeafa38490226a560ee02de89829a5b20
  8. CPU scheduling CPU scheduler responsible for proper processes planning: Sysctl:

    • kernel.sched_migration_cost_ns = 5000000 (default: 500000). • kernel.sched_autogroup_enabled = 0 (default: 1). http://www.postgresql.org/message-id/[email protected] http://kernelnewbies.org/Linux_2_6_38#head-59575a6aeafa38490226a560ee02de89829a5b20 Be aware on Ubuntu: 12.04 #1055222 and 14.04 #1422016. Use noautogroup kernel param instead of sysctl.conf.
  9. Virtual Memory Sysctl: vm.dirty_background_ratio & vm.dirty_ratio = disable it. vm.dirty_background_bytes

    & vm.dirty_bytes = depends on ... RAID cache size, 64MB/128MB otherwise
  10. NUMA BIOS: enable memory node interleaving. Kernel boot: numa=off. numactl

    utility. Sysctl: • vm.zone_reclaim_mode = 0 (default: 0). • kernel.numa_balancing = 0 (default: 0).
  11. Huge Pages Huge pages vs. Transparent huge pages. Huge pages

    are supported by many RDBMS. Always disable transparent huge pages.
  12. Huge Pages Huge pages vs. Transparent huge pages. Huge pages

    are supported by many RDBMS. Always disable transparent huge pages. /etc/rc.local: • echo never > /sys/kernel/mm/transparent_hugepage/enabled • echo never > /sys/kernel/mm/transparent_hugepage/defrag
  13. Filesystems Ext3 vs Ext4 vs XFS: what is better? Filesystem

    Barriers. Disable Write Cache: • hdparm -W0 /dev/device • MegaCli64 -LDSetProp -DisDskCache -Lall -aALL
  14. Filesystems Ext3 vs Ext4 vs XFS: what is better? Filesystem

    Barriers. Disable Write Cache: • hdparm -W0 /dev/device • MegaCli64 -LDSetProp -DisDskCache -Lall -aALL Hardware RAID + BBU = barrier=0 (disable). Software RAID = barrier=1 (enable).
  15. Filesystems Ext3 vs Ext4 vs XFS: what is better? Filesystem

    Barriers. Disable Write Cache: • hdparm -W0 /dev/device • MegaCli64 -LDSetProp -DisDskCache -Lall -aALL Hardware RAID + BBU = barrier=0 (disable). Software RAID = barrier=1 (enable). Enterprise SSD with Power Loss Protection = barrier=0 (disable).
  16. Storage IO SATA/SAS vs SSD. IO elevators: • noop: SSD,

    PCIe SSD, hi-end storages. • deadline: RAID, SATA/SAS. • cfq: good default. • none (multi-queue block IO): SSD, PCIe SSD.
  17. Storage IO SATA/SAS vs SSD. IO elevators: • noop: SSD,

    PCIe SSD, hi-end storages. • deadline: RAID, SATA/SAS. • cfq: good default. • none (multi-queue block IO): SSD, PCIe SSD. # echo 'elevator_name' > /sys/block/<device>/queue/scheduler kernel boot: elevator=<name> /sys/block/*/queue/: rotational, rq_affinity, read_ahead_kb
  18. Power Saving Policy Drivers: acpi_cpufreq vs. intel_pstate. scaling_governor: • /sys/devices/system/cpu/cpuX/cpufreq/scaling_available_governors

    • /sys/devices/system/cpu/cpuX/cpufreq/scaling_governor acpi_cpufreq + performance. intel_pstate + powersave.
  19. Misc: Clocksources What is clocksource? acpi_pm vs. hpet vs. tsc.

    /sys/devices/system/clocksource/clocksource0/available_clocksource. /sys/devices/system/clocksource/clocksource0/current_clocksource.
  20. Summary Linux is a good choice for RDBMS: Modern, Universal,

    Flexible, Stable. Adapt Linux for your workloads. Test → Change → Test → Commit/Rollback.