This is an implementation of temperature based object eviction policy for cache tiering. The current eviction policy is based only on the latest access time, without considering the access frequency in the history. This policy is apt to leave the just-accessed object in the cache pool, even it will no longer be accessed. Obviously, this policy will make bad choices in some scenarios. This motivates us to present temperature based object eviction policy, which makes eviction decision by considering both latest access time and access frequency, while keeping the simplicity of the current algorithm framework, and making minimal revision to it. The algorithm is simple, associate each hitset with a weight, the latest hitset with the heaviest weight, say, 1000000. And the least latest hitset with a lighter weight, decayed by an user-defined factor, say, 50, then the least latest hitset has a weight of 1000000*(100-50)/100=500000, and so on. Each object in the cache pool will be calculated a total weight according to its appearance in all the hitsets, then those objects with the least total weights are chosen as the eviction candidates. In fact, the algorithm reduces to the current atime based eviction policy by setting decay rate be 100. The patches: https://github.com/ceph/ceph/pull/4737 MingXin Liu (5): Osd: add three fields to pg_pool_t Mon: expose commands for temperature related setting Osd: add a temperature based object eviction policy for cache tiering Mon: add temperature support for existing cache related commands Doc: add temperature related stuff in documents and test scripts doc/dev/cache-pool.rst | 4 ++ doc/man/8/ceph.rst | 12 +++-- doc/rados/operations/pools.rst | 7 +++ qa/workunits/cephtool/test.sh | 14 ++++++ src/common/config_opts.h | 2 + src/mon/MonCommands.h | 8 ++- src/mon/OSDMonitor.cc | 101 ++++++++++++++++++++++++++++++++++--- src/osd/ReplicatedPG.cc | 110 ++++++++++++++++++++++------------------- src/osd/osd_types.cc | 32 +++++++++++- src/osd/osd_types.h | 49 ++++++++++++++++++ 10 files changed, 274 insertions(+), 65 deletions(-) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
