Hi Dylan,
That's a good find! Thanks for sharing the paper. I have dealt with the eviction policy code a little bit. Would you mind describing the issues first? As far as I know, the referencing and de-referencing of blocks is serial and sometimes causes performance bottlenecks. We may need to analyze if the bottlenecks are due to the eviction algorithm or synchronization involved in the eviction policy code. I tried the following fix https://github.com/hbdeshmukh/incubator-quickstep/commit/4b32336a1b89f70d1c17ffe7956ae6f78e691d7c to make the synchronization a bit fine grained and it helped a bit. Please feel free to adopt this fix. As a separate discussion, we have a complicated buffer management problem for following reasons. I am not sure if the current LRU-k eviction implementation addresses these concerns: 1. Blocks could be of different sizes and have different lifetimes (stored vs temporary). Therefore the consequences of evicting different blocks could be different. 2. We currently do not evict join hash tables. When memory is really scarce, the buffer pool should evict hash tables. How much attention should we pay to buffer management is more of a strategic decision, considering that our focus is on in-memory settings. Thanks, Harshad ________________________________ From: Dylan Bacon <dba...@wisc.edu> Sent: Friday, April 27, 2018 2:07:14 PM To: dev@quickstep.incubator.apache.org Subject: Eviction Policy Algorithm Attached screenshot of an algorithm that seems worthwhile to implement in Quickstep for an eviction policy. The language and structure would need to be adapted from cache pages to our database blocks, I'm not sure how straightforward that would be. Sending this to the dev email for broader discussion as I initially sent to individuals. Thoughts and input are welcome. Source paper: http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=C660AD720FD52C67A063B270F4B6DDF4?doi=10.1.1.105.6057&rep=rep1&type=pdf -- Regards, Dylan Bacon University of Wisconsin - Madison Department of Computer Sciences dba...@wisc.edu
