Troubleshooting
Problem
Transparent Huge Pages (THP) may cause high CPU utilization and performance issues on IBM Smart Analytics System 5600 environments using SUSE Linux Enterprise Server (SLES) 11 SP2
Symptom
When you are running into the THP performance problems, you often can see peaks in the CPU usage and a very high value of system time (sys-time) in relation to the user time (usr-time).
Environment
SUSE Linux Enterprise Server 11 SP2
Diagnosing The Problem
On systems with large memory, frequent access to the Translation Lookaside Buffer (TLB) may slow down the system significantly.
Transparent huge pages thus are of most use on systems with very large (128GB or more) memory, and help to drive performance. In SUSE Linux Enterprise, THP is enabled by default where it is expected to give a performance boost to a large number of workloads.
There are cases where THP may regress performance, particularly when under memory pressure due to pages being reclaimed in an effort to promote to huge pages. It is also possible that performance will suffer on CPUs with a limited number of huge page TLB entries for workloads that sparsely reference large amounts of memory.
Resolving The Problem
If necessary, THP can be disabled via the sysfs file "/sys/kernel/mm/transparent_hugepage/enabled", which accepts one of the values "always", "madvise", or "never".
To disable THP via sysfs and confirm it is disabled, do the following as root:
# echo never > /sys/kernel/mm/transparent_hugepage/enabled
# cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]
Related Information
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Document Information
Modified date:
16 June 2018
UID
swg21677458