mincore() & fincore()

["Cédric Villemain" <cedric@2ndquadrant.com>]

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Hello

First, the proposed changes in this email are to be used at least for 
PostgreSQL extensions, maybe for core.

Purpose is to offer better monitoring/tracking of the hot/cold areas (and 
read/write paterns) in the tables and indexes, in PostgreSQL those are by default 
written in segments of 1GB.

There are some possible usecase already:

 * planning of hardware upgrade
 * easier configuration setup (both PostgreSQL and linux)
 * provide more informations to the planner/executor of PostgreSQL

My ideas so far are to 

 * improve mincore() in linux and add it information like in freeBSD (at 
   least adding 'mincore_modified' to track clean vs dirty pages).
 * adding fincore() to make the information easier to grab from PostgreSQL (no 
   mmap)
 * maybe some access to those stats in /proc/

It makes years that libprefetch, mincore() and fincore() are discussed on linux 
mailling lists. And they got a good feedback... So I hope it is ok to keep on 
those and provide updated patches.

Johannes, I add you in CC because you're the last one who proposed something. Should I update your patch ?

-- 
Cédric Villemain +33 (0)6 20 30 22 52
http://2ndQuadrant.fr/
PostgreSQL: Support 24x7 - Développement, Expertise et Formation

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