This has been discussed before, but I couldn't find any bugs or mailing list threads that specifically dealt with it, so I thought I'd open up a formal feature request. Basically we would like to use the read and write caches, but don't want them to take up all the memory. We'd like to be able to keep a large amount of memory available for the block bitmaps and other OST ext metadata, without having to pin everything in memory with vfs_cache_pressure=0.

How much control is there in the Linux page cache? Is it possible to tell it to start flushing the object caches if they start taking up X amount of space?