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List:       suse-linux-e
Subject:    RE: [SLE] OO: If you can make it, I can break it!
From:       "Carlos E. R." <robin1.listas () tiscali ! es>
Date:       2005-12-31 11:04:07
Message-ID: Pine.LNX.4.61.0512311151040.4342 () nimrodel ! valinor
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The Friday 2005-12-30 at 16:53 -0900, Greg Wallace wrote:

> >Correct; but not only binaries, but everything.
> 
> But just the read only portion is cached, right? 

No, also the write operations are cached. I understand that the kernel 
then sorts the pending write operations to try minimize disk head 
movements (I saw somewhere keywords to select the sorting algorithm). You 
can dissable write cache operations with the option "sync" in fstab; for 
example, if you automount media like floppies or external drives, they are 
normally mounted sync, so they can be removed fast: but they are slow when
writing because the cache is dissabled, mounted sync.

 The working copy
> (temporary storage holding values you input but not saved) is modified by
> what you do while you're modifying a data file but that doesn't change
> what's cached.  The cached copy is just a blank slate, suitable for a pure
> memory to memory copy if you exit the app and then call it back up.  I
> wouldn't think that any special/seldom used forms would be loaded by default
> either, but would only be loaded if you actually went to one of those during
> your edit session.  Probably just the initial form that you see when you
> start the app (and maybe a few commonly used ones) is loaded when you call
> up the app the first time.

No, the cache doesn't know about forms or any application internals. It 
just copies the disk sectors or files into memory and operates there, in 
memory. If the cache is dirty, modified, then it will be saved to disk 
promptly, but not inmediately. It is not only binaries, but any file.

For the exact details, you would have to ask a kernel developper :-)

- -- 
Cheers,
       Carlos Robinson

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