| config ZCACHE |
| bool "Dynamic compression of swap pages and clean pagecache pages" |
| depends on CRYPTO=y && SWAP=y && CLEANCACHE && FRONTSWAP |
| select CRYPTO_LZO |
| default n |
| help |
| Zcache doubles RAM efficiency while providing a significant |
| performance boosts on many workloads. Zcache uses |
| compression and an in-kernel implementation of transcendent |
| memory to store clean page cache pages and swap in RAM, |
| providing a noticeable reduction in disk I/O. |
| |
| config RAMSTER |
| bool "Cross-machine RAM capacity sharing, aka peer-to-peer tmem" |
| depends on CONFIGFS_FS=y && SYSFS=y && !HIGHMEM && ZCACHE=y |
| depends on NET |
| # must ensure struct page is 8-byte aligned |
| select HAVE_ALIGNED_STRUCT_PAGE if !64_BIT |
| default n |
| help |
| RAMster allows RAM on other machines in a cluster to be utilized |
| dynamically and symmetrically instead of swapping to a local swap |
| disk, thus improving performance on memory-constrained workloads |
| while minimizing total RAM across the cluster. RAMster, like |
| zcache2, compresses swap pages into local RAM, but then remotifies |
| the compressed pages to another node in the RAMster cluster. |
| |
| # Depends on not-yet-upstreamed mm patches to export end_swap_bio_write and |
| # __add_to_swap_cache, and implement __swap_writepage (which is swap_writepage |
| # without the frontswap call. When these are in-tree, the dependency on |
| # BROKEN can be removed |
| config ZCACHE_WRITEBACK |
| bool "Allow compressed swap pages to be writtenback to swap disk" |
| depends on ZCACHE=y && BROKEN |
| default n |
| help |
| Zcache caches compressed swap pages (and other data) in RAM which |
| often improves performance by avoiding I/O's due to swapping. |
| In some workloads with very long-lived large processes, it can |
| instead reduce performance. Writeback decompresses zcache-compressed |
| pages (in LRU order) when under memory pressure and writes them to |
| the backing swap disk to ameliorate this problem. Policy driving |
| writeback is still under development. |
