Tuning Linux for Databases.
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This presentation discusses optimizing Linux systems for PostgreSQL databases. Linux is a good choice for databases due to its active development, features, stability, and community support. The presentation covers optimizing various system resources like CPU scheduling, memory, storage I/O, and power management to improve database performance. Specific topics include disabling transparent huge pages, tuning block I/O schedulers, and selecting appropriate scaling governors. The overall message is that Linux can be adapted for database workloads through testing and iterative changes.
Tuning Linux for Databases.
- 2. 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
- 3. 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.
- 4. Why Linux? Linux is a good choice: ● Active development & Community support. ● A lot of features & Fast implementation. ● Stable & Mature & Durable.
- 5. 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
- 6. Databases & Resources CPU Scheduling NUMA Power Saving Virtual Memory NUMA Huge Pages File Systems Storage I/O CPU Memory Storage
- 7. Resources CPU scheduler. Virtual memory and NUMA. Huge pages. File systems. Storage IO. Power saving policy. Others.
- 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
- 9. 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.
- 10. Virtual Memory What is it? Allocator, Caching, Dirty pages and Writeback.
- 11. Virtual Memory
- 12. 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
- 13. Virtual Memory Out-of-memory & OOM-Killer Sysctl: vm.swappiness = 1 (default: 60)
- 14. NUMA S — Socket C — CPU core M — Memory bank
- 15. 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).
- 16. Huge Pages Huge pages vs. Transparent huge pages. Huge pages are supported by many RDBMS. Always disable transparent huge pages.
- 17. 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
- 18. Filesystems Ext3 vs Ext4 vs XFS: what is better? Filesystem Barriers.
- 19. Filesystems Ext3 vs Ext4 vs XFS: what is better? Filesystem Barriers. Disable Write Cache: ● hdparm -W0 /dev/device ● MegaCli64 -LDSetProp -DisDskCache -Lall -aALL
- 20. 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).
- 21. 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).
- 22. Storage IO SATA/SAS vs SSD. IO elevators.
- 23. 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.
- 24. 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
- 25. Power Saving Policy Drivers: acpi_cpufreq vs. intel_pstate. scaling_governor.
- 26. 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
- 27. 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.
- 28. 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.
- 29. Summary Linux is a good choice for RDBMS: Modern, Universal, Flexible, Stable. Adapt Linux for your workloads. Test → Change → Test → Commit/Rollback.
- 30. Questions? Alexey Lesovsky [email protected] PostgreSQL-Consulting.com: Data maintenance at its best https://postgresql-consulting.com