Hello all, Sorry if this is a naive question.
I was going through Greg Smith's slides on buffer cache(http://www.westnet.com/~gsmith/content/postgresql/InsideBufferCache.pdf). When going through the page replacement algorithm that we use i.e. clocksweep algorithm, I felt a potential problem in our current system. Specifically, when a new entry is allocated in the buffer, it's USAGE_COUNT is set to 1. On each sweep of the algorithm, the USAGE_COUNT is decremented and an entry whose USAGE_COUNT becomes zero is replaced. I feel that this could lead to a bias towards replacement of relatively younger pages in the cache over older pages. An entry which has just entered the cache with USAGE_COUNT=1 could be replaced soon, but it may be needed frequently in the near future, which would result in it being repeatedly brought into the cache, leading to replacement overheads. I think this is the well known face off between LRU and MRU algorithms. How do we work around this problem? Regards, Atri -- Regards, Atri l'apprenant -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
