Timesten: Linux System Virtual Memory Parameters and TimesTen Performance
Last updated on SEPTEMBER 23, 2016
Applies to:Oracle TimesTen In-Memory Database - Version 11.2.1 and later
Red Hat Enterprise Linux Workstation
Currency check 16-oct-2014
There are a series of Linux kernel parameters affecting various virtual memory functions in Linux. I will refer to these as the "vm. parameters". These parameters include the following:
- vm.swappiness: a property of the kernel that changes the balance between swapping out runtime memory, as opposed to dropping pages from the system page cache. Swappiness can be set to values between 0 and 100 inclusive. The default is 60.
- vm.dirty_background_ratio: defines the point at which the linux kernel start the background task of writing out dirty pages. Default is 60%
- vm.dirty_ratio: defines the percentage of dirty pages in all of system memory at which point the process itself writes data to disk files (synchronous writes) rather than letting the asynchronous kernel background process "pdflush" write to disk. Default is 40.
- vm.dirty_expire_centisecs: defines when dirty data is old enough to be eligible for writeout by the pdflush daemons. It is expressed in 100'ths of a second. Data which has been dirty in-memory for longer than this interval will be written out next time a pdflush daemon wakes up. Default is 3000
- vm.dirty_writeback_centisecs: the sleep interval of the pdflush daemon, expressed in 100'ths of a second. The default is 500
Can changing the values of the vm. parameters have an impact on TimesTen performance?
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