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List:       user-mode-linux-devel
Subject:    Re: [uml-devel] Re: madvise(DONTNEED) on tmpfs pages instead of /dev/anon
From:       Blaisorblade <blaisorblade () yahoo ! it>
Date:       2005-08-26 15:06:20
Message-ID: 200508261706.20923.blaisorblade () yahoo ! it
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On Monday 22 August 2005 22:24, Jeff Dike wrote:
> On Fri, Aug 12, 2005 at 07:00:26PM +0200, Blaisorblade wrote:
> > Yes, but for the VM, there is nothing else than pagecache and swapcache
> > and swap entries. Since that call will drop them, on normal files backing
> > store will remain, on tmpfs everything will vanish!

> > Hope you'll implement this soon, if it works.

> There was a small omission in my quick analysis, which you alluded to
> above.

> It's removed from the address space, but preserved in the page cache.
Yes, yesterday I realized this point. The pagecache has one additional 
reference, which is only deleted after try_to_unmap() (the rmap function to 
detach a page from page tables) succeeds (grep try_to_unmap mm/*.c to find 
the caller).

In fact, the madvise() comment only talks about anonymous memory.

Rik, is there any hope to extend madvise() to cater for this?
> Run the test below to see this.
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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