lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 16 Apr 2019 07:30:20 -0700
From:   Dave Hansen <>
To:     Michal Hocko <>,
        Yang Shi <>
Subject: Re: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node

On 4/16/19 12:47 AM, Michal Hocko wrote:
> You definitely have to follow policy. You cannot demote to a node which
> is outside of the cpuset/mempolicy because you are breaking contract
> expected by the userspace. That implies doing a rmap walk.

What *is* the contract with userspace, anyway? :)

Obviously, the preferred policy doesn't have any strict contract.

The strict binding has a bit more of a contract, but it doesn't prevent
swapping.  Strict binding also doesn't keep another app from moving the

We have a reasonable argument that demotion is better than swapping.
So, we could say that even if a VMA has a strict NUMA policy, demoting
pages mapped there pages still beats swapping them or tossing the page
cache.  It's doing them a favor to demote them.

Or, maybe we just need a swap hybrid where demotion moves the page but
keeps it unmapped and in the swap cache.  That way an access gets a
fault and we can promote the page back to where it should be.  That
would be faster than I/O-based swap for sure.

Anyway, I agree that the kernel probably shouldn't be moving pages
around willy-nilly with no consideration for memory policies, but users
might give us some wiggle room too.

Powered by blists - more mailing lists