ComputerStuff‎ > ‎

LinuxVMtuning


/proc/sys/vm  hierarchy

Swappiness

swappiness is a parameter which sets the kernel's balance between reclaiming pages from the page cache and swapping process memory. The default value is 60.

If you want kernel to swap out more process memory and thus cache more file contents increase the value. Otherwise, if you would like kernel to swap less decrease it.


vfs_cache_pressure

Controls the tendency of the kernel to reclaim the memory which is used for caching of directory and inode objects.

At the default value of vfs_cache_pressure = 100 the kernel will attempt to reclaim dentries and inodes at a "fair" rate with respect to pagecache and swapcache reclaim. Decreasing vfs_cache_


overcommit_memory

Controls overcommit of system memory, possibly allowing processes to allocate (but not use) more memory than is actually available.

  • 0 - Heuristic overcommit handling. Obvious overcommits of address space are refused. Used for a typical system. It ensures a seriously wild allocation fails while allowing overcommit to reduce swap usage. root is allowed to allocate slighly more memory in this mode. This is the default.
  • 1 - Always overcommit. Appropriate for some scientific applications.
  • 2 - Don't overcommit. The total address space commit for the system is not permitted to exceed swap plus a configurable percentage (default is 50) of physical RAM. Depending on the percentage you use, in most situations this means a process will not be killed while attempting to use already-allocated memory but will receive errors on memory allocation as appropriate.\\

overcommit_ratio

Percentage of physical memory size to include in overcommit calculations.

Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100)

swapspace = total size of all swap areas
physmem = size of physical memory in system


IBM nmon

http://www.ibm.com/developerworks/aix/library/au-analyze_aix/




Comments