Re: Subtle MM bug

[Marcelo Tosatti <marcelo@conectiva.com.br>]

On Tue, 9 Jan 2001, Linus Torvalds wrote:

> Hmm.. Fair enough. However, if you don't have VM pressure, you're also not
> going to look at the page tables, so you are not going to get any use
> information from them, either.

Are you sure that potentially unmapping pte's and swapping out its pages
in the background scanning is ok? 

I mean, what kind of swap behaviour we will have if we do it?

> The aging should really be done at roughly the same rate as the "mark
> active", wouldn't you say? If you mark things active without aging, pages
> end up all being marked as "new". And if you age without marking things
> active, they all end up being "old". Neither is good. What you really want
> to have is aging that happens at the same rate as reference marking.
> So one "conditional aging" algorithm might just be something as simple as
> 
>  - every time you mark something referenced, you increment a counter
>  - every time you want to age something, you check whethe rthe counter is
>    positive first (and decrement it if you age something)

Seems to be a nice solution.

I'll send you the previously promised patch and then I'll send the
background scanning one as soon as we (or I?) figure out the previous
question about background pte scanning.


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux.eu.org/Linux-MM/