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

[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:

quoted

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