psim is a Linux memory subsystem simulator used for evaluating memory squeezing algorithms.
It simulates a VM performing a workload and measures the amount of work done in a given time.
For every simulator tick:
- the workload determines which memory page the vCPU accesses
- accessing a free or unmapped page incurs a minor fault, blocking the vCPU from doing work for a short time;
- accessing a paged-out page incurs a major fault, blocking the vCPU from doing work for a prolonged time;
- the vCPU does a unit of work on the page.
Linux memory subsystem behaviour is simulated:
- Periodically scan memory to update active/inactive lists according to page accesses since last scan
- inactive pages are candidates for paging out
- page out if the number of allocated pages exceeds the memory limit.
Further reading: Mel Gorman, Understanding the Linux Virtual Memory Manager (chapter 10), http://www.kernel.org/doc/gorman/.
- psim.py -- executable for running simulator
- host.py -- host memory simulator core
- workload.py -- contains various workload models
- squeezer.py -- contains various memory squeezer algorithm implementations
Running psim requires python-matplotlib.
Example command-line: python psim.py --memory=128 --ticks=1000000 --squeezer=mk2
Example output:
