The conventional io hints by fadvise() is to give chance for applications to manipulate page cache. This patch extends io hint ability to control cache pool behavior to avoid cache pollution. For example, under WRITEBACK mode, consider the following operation series, WRITE A; WRITE B; READ A, if B is never accessed later, then the write of B pollutes the cache by forcing A evicted, the reuse of A causes a cache miss. With the io hint, we could explicitly tell rados to not to cache B, thereby avoid cache pollution.
The patches: https://github.com/ceph/ceph/pull/4754 Min Chen (2): Rados: cache-tierng support CEPH_OP_FLAG_TIER_NOCACHE Rados: add test case for CEPH_OP_FLAG_TIER_NOCACHE src/include/rados.h | 1 + src/include/rados/librados.h | 1 + src/include/rados/librados.hpp | 1 + src/librados/librados.cc | 2 + src/osd/ReplicatedPG.cc | 5 ++ src/osd/osd_types.cc | 1 + src/test/librados/tier.cc | 176 +++++++++++++++++++++++++++++++++++++++++ 7 files changed, 187 insertions(+) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
