Re: mm question

On 11 Dec 2001, Eric W. Biederman wrote:

> [e-mail] writes:
> 
> > On Mon, 10 Dec 2001, Alan Cox wrote:
> > 
> > > > Right, but instead of trying to balance cache available memory and swap
> > > > my swapper will only be concerned whether the page can be evicted and
> > > > whether it is from the address range I want.
> > > 
> > > You want to rewrite the entire vm to have back pointers ? Right now you
> > > can't find pages in an address range. Its all driven from the virtual side
> > > without reverse lookup tables.
> > > 
> > 
> > You are right I don't want to rewrite vm. But I can go thru virtual side
> > taking note of the physical address. I.e. base the decision to try and
> > free pages not on how old the page is but on what it's physical address
> > is.
> > 
> > You see, I don't want to find a few pages in 16mb range in 512mb system.
> > 
> > I want to find a few pages _outside_ 64mb range in a 512mb system. 
> > So if I free 70mb I _will_ be able to find at least 2mb in my desired
> > range. In fact I won't have to free that much as they it will work is
> > "try to free the page", "if succeed do not return to memory pool but
> > instead give to the 'special region list'"
> > 
> > Does this make sense ?
> 
> There is actually a cheap trick that will achieve what you want.
> Allocate pages.  If you allocate a page in the 0-64mb range keep
> it allocated until you have allocated your 300KB > 64mb.  After
> you have all of the pages you want free the extra pages in 0-64mb that
> you didn't want...

Yes, I thought of that, but this might produce more memory pressure than
needed. 

Regardless, it looks like I won't need this after all - the device has
internal memory controller which was misprogrammed. I think I corrected
this so it looks to be working now.

However, the question of how to get pages from a given range is
interesting in itself..

                 big thanks to everyone who responded :))

                            Vladimir Dergachev

> 
> Eric
>