Re: [RFC 0/7] introduce memory hinting API for external process

[Michal Hocko]

[linux-api]

On Mon 20-05-19 18:44:52, Matthew Wilcox wrote:
> On Mon, May 20, 2019 at 12:52:47PM +0900, Minchan Kim wrote:
> > IMHO we should spell it out that this patchset complements MADV_WONTNEED
> > and MADV_FREE by adding non-destructive ways to gain some free memory
> > space. MADV_COLD is similar to MADV_WONTNEED in a way that it hints the
> > kernel that memory region is not currently needed and should be reclaimed
> > immediately; MADV_COOL is similar to MADV_FREE in a way that it hints the
> > kernel that memory region is not currently needed and should be reclaimed
> > when memory pressure rises.
> 
> Do we tear down page tables for these ranges?  That seems like a good
> way of reclaiming potentially a substantial amount of memory.

I do not think we can in general because this is a non-destructive
operation. So at least we cannot tear down anonymous ptes (they will
turn into swap entries).

-- 
Michal Hocko
SUSE Labs