HBASE-27867 Close the L1 victim handler race #5239
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I checked out the branch I pushed and ran The test issue is not a unit test failure and does not appear to be related to this change. Looks like we may need to do a zombie cleanup. |
Apache9
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May 17, 2023
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/LruBlockCache.java
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virajjasani
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When we evict a block from L1 and move it to L2 there is a brief window of time where we have removed the block from the L1 map and yet the victim handler has not completed execution. Some read-your-write use cases can be significantly impacted even though the window is small. Victim handling can be made atomic with respect to the unmapping operation. The upside is there will be no L1+L2 misses during the transition. The downside is if the victim handler takes a long time to execute – currently they are all very fast, so only a theoretical risk – then other removals or insertions in L1 can block until it completes.
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Rebased. Addressed review feedback. |
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virajjasani
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May 18, 2023
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@Apache9 please let me know if you have any more concerns or nits. I plan to merge this tomorrow. |
Apache9
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May 21, 2023
asfgit
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May 26, 2023
When we evict a block from L1 and move it to L2 there is a brief window of time where we have removed the block from the L1 map and yet the victim handler has not completed execution. Some read-your-write use cases can be significantly impacted even though the window is small. Victim handling can be made atomic with respect to the unmapping operation. The upside is there will be no L1+L2 misses during the transition. The downside is if the victim handler takes a long time to execute – currently they are all very fast, so only a theoretical risk – then other removals or insertions in L1 can block until it completes. Signed-off-by: Duo Zhang <zhangduo@apache.org> Signed-off-by: Viraj Jasani <vjasani@apache.org>
asfgit
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May 26, 2023
When we evict a block from L1 and move it to L2 there is a brief window of time where we have removed the block from the L1 map and yet the victim handler has not completed execution. Some read-your-write use cases can be significantly impacted even though the window is small. Victim handling can be made atomic with respect to the unmapping operation. The upside is there will be no L1+L2 misses during the transition. The downside is if the victim handler takes a long time to execute – currently they are all very fast, so only a theoretical risk – then other removals or insertions in L1 can block until it completes. Signed-off-by: Duo Zhang <zhangduo@apache.org> Signed-off-by: Viraj Jasani <vjasani@apache.org>
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When we evict a block from L1 and move it to L2 there is a brief window of time where we have removed the block from the L1 map and yet the victim handler has not completed execution. Some read-your-write use cases can be significantly impacted even though the window is small. Victim handling can be made atomic with respect to the unmapping operation. The upside is there will be no L1+L2 misses during the transition. The downside is if the victim handler takes a long time to execute – currently they are all very fast, so only a theoretical risk – then other removals or insertions in L1 can block until it completes.