Re: [Firebird-devel] MaxFileSystemCache (was Re: FB 2.1 64bit and memory usage ??)

[Vlad H. <hv...@us...>]

> >> Testing the new feature, I see a problem.
> >>
> >> Since we maintain the cache per-database, when all attachments are 
> >> disconnected, we loose all the cache, causing very huge performance 
> >> problems.
> >>     
> >
> >     How it is related to the new feature ?
> Not directly related, but with FS cache enabled, the OS caches even 
> closed files.

    Yes, for some time.
 
> This is big problem with FS cache disabled...

    I.e. you disabled it explicitly for some database ? 
 
> Imagine all users disconnect from application in the end of day and 
> reconect again in the another day.

    Do you think OS will retain FS cache over the night ? ;) It must be not 
a very busy server ;) 

> Just for example, I have a query that runs in 250 seconds when database 
> is not cached, and 3 seconds when it is cached (i.e., run it again even 
> if I close the server).

    And what ? 

    This feature :

a) disabled by default. To enable it you must set page buffers for some (or 
    all) database more than 65536 (not a very common value, isn't is ?) or 
    set MaxFileSystemCache to some small value (less than 2048, by default). 

b) If you decide to use it - you must understand what you do

    I'll write short guide how and when to use it

Regards,
Vlad