9.4. Memory
9.4.1. Virtual Memory Parameters
- vm.dirty_ratio
- vm.dirty_background_ratio
Table 9.1. Recommended Values for Virtual Memory Parameters
I/O Type | Recommended Value | Remarks |
---|---|---|
Large file sequential I/O workloads | dirty_ratio = 20, dirty_background_ratio = 10 (default setting) | The writeback operations to disk are efficient for this workload therefore the Virtual Memory parameters can have higher values. Higher values for these parameters help reduce fragmentation of large files with thin-provisioned storage.. |
Random and small file workloads | dirty_ratio = 5, dirty_background_ratio = 2 | The write operations to disk are less efficient for this workload. Lower values of the Virtual Memory parameters prevent excessive delays during write-back. |
The Red Hat Storage tuned
profiles, rhs-high-throughput
and rhs-virtualization
, permit custom settings for system parameters in the file /etc/sysctl.conf
.
- Edit the file
/etc/sysctl.conf
to update the parameters with the desired values in the file.Example 9.1. Update the Virtual Memory Parameters
vm.dirty_ratio = 5 vm.dirty_background_ratio = 2
- Execute the
tuned-adm
command to apply these values:# tuned-adm profile PROFILE-NAME
Example 9.2. Applying Virtual Memory Parameters
In this example,rhs-high-throughput
is the profile which is being activated.# tuned-adm profile rhs-high-throughput
- Verify the changes made to the virtual Memory parameters.
# cat /proc/sys/vm/dirty_ratio 5 # cat /proc/sys/vm/dirty_background_ratio 2