osd/ReplicatedPG: fix promotion recency logic #6702
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Two small nits, otherwise looks good to me! |
Recency is defined as how many of the last N hitsets an object must appear in in order to be promoted. The previous logic did nothing of the sort... it checked for the object in any one of the last N hitsets, which led to way to many promotions and killed any chance of the cache performing properly. While we are here, we can simplify the code to drop the max_in_* fields (no longer necessary). Note that we may still want a notion of 'temperature' that does tolerate the object missing in one of the recent hitsets.. but that would be different than recency, and should probably be modeled after the eviction temperature model. Backport: infernalis, hammer Reported-by: Nick Fisk <nick@fisk.me.uk> Signed-off-by: Sage Weil <sage@redhat.com>
Reported-by: xinxin shu <xinxin.shu@intel.com> Signed-off-by: Sage Weil <sage@redhat.com>
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@liewegas how do you think about back-porting this to hammer branch? I can do the work if you think it's OK. |
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Yeah, I think it's an important backport! THanks
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Backport ceph#6702 (osd/ReplicatedPG: fix promotion recency logic) to Hammer. Signed-off-by: Yuan Zhou <yuan.zhou@intel.com>
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Backport ceph#6702 (osd/ReplicatedPG: fix promotion recency logic) to Hammer. Signed-off-by: Yuan Zhou <yuan.zhou@intel.com>
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osd/ReplicatedPG: fix promotion recency logic Reviewed-by: Samuel Just <sjust@redhat.com>
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http://tracker.ceph.com/issues/14320
Recency is defined as how many of the last N hitsets an object
must appear in in order to be promoted. The previous logic did
nothing of the sort... it checked for the object in any one of
the last N hitsets, which led to way to many promotions and killed
any chance of the cache performing properly.
While we are here, we can simplify the code to drop the max_in_*
fields (no longer necessary).
Note that we may still want a notion of 'temperature' that does
tolerate the object missing in one of the recent hitsets.. but
that would be different than recency, and should probably be
modeled after the eviction temperature model.
Backport: infernalis, hammer
Reported-by: Nick Fisk nick@fisk.me.uk
Signed-off-by: Sage Weil sage@redhat.com