Le samedi 24 octobre 2009 01:04:19, Josh Berkus a écrit : > Cedric, > > > ase is a table containing 29 GB of bytea in a database of 52 GB. Every > > row on the 29GB table is grab only few times. And it will just renew OS > > cache memory every time (the server have only 8GB of ram). > > So when I remove this table (not the index) from the OS cache memory, I > > keep more interesting blocks in the OS cache memory. > > effective_cache_size doesn't control what gets cached, it just tells the > planner about it. > > Now, if we had an OS which could be convinced to handle caching > differently for different physical devices, then I could see wanting > this setting to be per-tablespace. For example, it would make a lot of > sense not to FS-cache any data which is on a ramdisk or superfast SSD > array. The same with archive data which you expected to be slow and > infrequently accessed on a NAS device. If your OS can do that, while > caching data from other sources, then it would make sense. > > However, I don't know any current OS which allows for this. Does anyone > else?
Isn't it what "fadvise -dontneed" let you do ? Josh, I talk about effective_cache_size per tablespace *exactly* for the reason you explain. -- Cédric Villemain Administrateur de Base de Données Cel: +33 (0)6 74 15 56 53 http://dalibo.com - http://dalibo.org
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