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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.
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