Performance best practices and configuration guidelines for SQL Server on Linux
This article provides best practices and recommendations to maximize performance for database applications that connect to SQL Server on Linux. These recommendations are specific to running on the Linux platform. All normal SQL Server recommendations, such as index design, still apply.
The following guidelines contain recommendations for configuring both SQL Server and the Linux operating system.
SQL Server configuration
It is recommended to perform the following configuration tasks after you install SQL Server on Linux to achieve best performance for your application.
Use PROCESS AFFINITY for Node and/or CPUs
It is recommended to use
ALTER SERVER CONFIGURATIONto set
PROCESS AFFINITYfor all the NUMANODEs and/or CPUs you are using for SQL Server (which is typically for all NODEs and CPUs) on a Linux Operating System. Processor affinity helps maintain efficient Linux and SQL Scheduling behavior. Using the NUMANODE option is the simplest method. Note, you should use PROCESS AFFINITY even if you have only a single NUMA Node on your computer. See the ALTER SERVER CONFIGURATION documentation for more information on how to set PROCESS AFFINITY.
Configure multiple tempdb data files
Because a SQL Server on Linux installation does not offer an option to configure multiple tempdb files, we recommend that you consider creating multiple tempdb data files after installation. For more information, see the guidance in the article, Recommendations to reduce allocation contention in SQL Server tempdb database.
The following recommendations are optional configuration settings that you may choose to perform after installation of SQL Server on Linux. These choices are based on the requirements of your workload and configuration of your Linux Operating System.
Set a memory limit with mssql-conf
In order to ensure there is enough free physical memory for the Linux Operating System, the SQL Server process uses only 80% of the physical RAM by default. For some systems which large amount of physical RAM, 20% might be a significant number. For example, on a system with 1 TB of RAM, the default setting would leave around 200 GB of RAM unused. In this situation, you might want to configure the memory limit to a higher value. See the documentation on the mssql-conf tool and the memory.memorylimitmb setting that controls the memory visible to SQL Server (in units of MB).
When changing this setting, be careful not to set this value too high. If you do not leave enough memory, you could experience problems with the Linux Operating System and other Linux applications.
Linux OS Configuration
Consider using the following Linux Operating System configuration settings to experience the best performance for a SQL Server Installation.
Kernel settings for high performance
These are the recommended Linux Operating System settings related to high performance and throughput for a SQL Server installation. See your Linux Operating System documentation for the process to configure these settings.
For Red Hat Enterprise Linux (RHEL) users, the tuned throughput-performance profile configure these settings automatically (except for C-States). Starting with RHEL 8.0, a /usr/lib/tuned built-in mssql profile was co-developed with Red Hat and offers finer Linux performance related tunings for SQL Server workloads. This profile includes the RHEL throughput-performance profile and we present its definitions below for your review with other Linux distros and RHEL releases without this profile.
The following table provides recommendations for CPU settings:
|CPU frequency governor||performance||See the cpupower command|
|ENERGY_PERF_BIAS||performance||See the x86_energy_perf_policy command|
|min_perf_pct||100||See your documentation on intel p-state|
|C-States||C1 only||See your Linux or system documentation on how to ensure C-States is set to C1 only|
The following table provides recommendations for disk settings:
|disk readahead||4096||See the blockdev command|
|sysctl settings||kernel.sched_min_granularity_ns = 10000000
kernel.sched_wakeup_granularity_ns = 15000000
vm.dirty_ratio = 40
vm.dirty_background_ratio = 10
vm.swappiness = 10
|See the sysctl command|
Kernel setting auto numa balancing for multi-node NUMA systems
If you install SQL Server on a multi-node NUMA systems, the following kernel.numa_balancing kernel setting is enabled by default. To allow SQL Server to operate at maximum efficiency on a NUMA system, disable auto numa balancing on a multi-node NUMA system:
sysctl -w kernel.numa_balancing=0
Kernel settings for Virtual Address Space
The default setting of vm.max_map_count (which is 65536) may not be high enough for a SQL Server installation. Change this value (which is an upper limit) to 256K.
sysctl -w vm.max_map_count=262144
Proposed Linux settings using a tuned mssql profile
# # A tuned configuration for SQL Server on Linux # [main] summary=Optimize for Microsoft SQL Server include=throughput-performance [cpu] force_latency=5 [sysctl] vm.swappiness = 1 vm.dirty_background_ratio = 3 vm.dirty_ratio = 80 vm.dirty_expire_centisecs = 500 vm.dirty_writeback_centisecs = 100 vm.transparent_hugepages=always # For , use # vm.transparent_hugepages=madvice vm.max_map_count=1600000 net.core.rmem_default = 262144 net.core.rmem_max = 4194304 net.core.wmem_default = 262144 net.core.wmem_max = 1048576 kernel.numa_balancing=0 kernel.sched_latency_ns = 60000000 kernel.sched_migration_cost_ns = 500000 kernel.sched_min_granularity_ns = 15000000 kernel.sched_wakeup_granularity_ns = 2000000
To enable this tuned profile, save these definitions in a tuned.conf file under a /usr/lib/tuned/mssql folder and enable the profile using
chmod +x /usr/lib/tuned/mssql/tuned.conf tuned-adm profile mssql
Verify its enabling with
Disable last accessed date/time on file systems for SQL Server data and log files
Use the noatime attribute with any file system that is used to store SQL Server data and log files. Refer to your Linux documentation on how to set this attribute.
Leave Transparent Huge Pages (THP) enabled
Most Linux installations should have this option on by default. We recommend for the most consistent performance experience to leave this configuration option enabled. However, in case of high memory paging activity in SQL Server deployments with multiple instances for example or SQL Server execution with other memory demanding applications on the server, we suggest testing your applications performance after executing the following command
echo madvice > /sys/kernel/mm/transparent_hugepage/enabled
or modifying the mssql tuned profile with the line
and make the mssql profile active after the modification
tuned-adm off tuned-adm profile mssql
Ensure you have a properly configured swapfile to avoid any out of memory issues. Consult your Linux documentation for how to create and properly size a swapfile.
Virtual Machines and Dynamic Memory
If you are running SQL Server on Linux in a virtual machine, ensure you select options to fix the amount of memory reserved for the virtual machine. Do not use features like Hyper-V Dynamic Memory.
To learn more about SQL Server features that improve performance, see Get started with Performance features.
For more information about SQL Server on Linux, see Overview of SQL Server on Linux.