Re: [highmem bug report against -test5 and -test6] Re: [PATCH] Re:simple FS application that hangs 2.4-test5, mem mgmt problem or FS buffercache mgmt problem? (fwd)

[Ingo Molnar <mingo@elte.hu>]

On Mon, 2 Oct 2000, Rik van Riel wrote:

> > yep, this would be nice, but i think it will be quite tough to
> > balance this properly. There are two kinds of bhs in this aging
> > scheme: 'normal' bhs (metadata), and 'virtual' bhs (aliased to a
> > page). Freeing a 'normal' bh will get rid of the bh, and will

> This is easy. Normal page aging will take care of the buffermem pages.
> Freeing the buffer heads on pagecache pages is the only thing we need
> to do in refill_inactive_scan.

to do some sort of aging is of course easy. But to treat a 4kbyte
'metadata bh' the same way as a 80 bytes worth 'cached mapping bh' is IMO
a stretch. This is what i ment by 'tough to balance properly'.

> > another thing is the complexity of marking a page dirty - right
> > now we can assume that page->buffers holds all the blocks. With
> > aging we must check wether a bh is there or not,
> 
> The code must already be able to handle this. This is nothing new.

sure this is new. The page->buffers list right now is assumed to stay
constant after being created.

> > i'd love to have all the cached objects within the system on a
> > global, size-neutral LRU list. (or at least attach a
> > last-accessed timestamp to them.) This way we could synchronize
> > the pagecache, inode/dentry and buffer-cache LRU lists.
> 
> s/LRU/page aging/   ;)

no - how does this handle the inode/dentry cache? Making everything a page
is a mistake.

	Ingo

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