Reduce memory scanning overhead with the lrubucket parameter

Tuning with the lrubucket parameter can reduce scanning overhead on large memory systems.

The page-replacement algorithm scans memory frames looking for a free frame. During this scan, reference bits of pages are reset, and if a free frame has not been found, a second scan is done. In the second scan, if the reference bit is still off, the frame will be used for a new page (page replacement).

On large memory systems, there may be too many frames to scan, so now memory is divided up into buckets of frames. The page-replacement algorithm will scan the frames in the bucket and then start over on that bucket for the second scan before moving on to the next bucket. The default number of frames in this bucket is 131072 or 512 MB of RAM. The number of frames is tunable with the command vmo -o lrubucket=new value, and the value is in 4 KB frames.