Large Buffer Cache

The buffer cache can now occupy as much free memory as is available, up to the system limit of 3.75 GB. Prior to 10.10, the implementation of the buffer cache silently limited the size to 1 GB.

The kernel parameters dbc_min_pct or bufpages can be set beyond 1 GB if that physical memory is available.

This change allows the storage of nearly 3.75 GB of file data in memory. This should produce a noticeable increase of speed for applications that access between 1 and 3.75 GB of file system data. There is one exception: NFS server code is unable to take advantage of a buffer cache over 1 GB due to limitations in the networking drivers.

If the kernel configuration requested, but previously did not receive, a buffer cache larger than 1 GB, the increase in size at 10.10 might change performance and response time, depending on the workload.