On Fri, Sep 21, 2018 at 4:51 PM Elliott, Robert (Persistent Memory) <elliott@xxxxxxx> wrote: > > > > -----Original Message----- > > From: linux-kernel-owner@xxxxxxxxxxxxxxx <linux-kernel- > > owner@xxxxxxxxxxxxxxx> On Behalf Of Kees Cook > > Sent: Friday, September 21, 2018 2:13 PM > > Subject: Re: [PATCH 0/3] mm: Randomize free memory > ... > > I'd be curious to hear more about the mentioned cache performance > > improvements. I love it when a security feature actually _improves_ > > performance. :) > > It's been a problem in the HPC space: > http://www.nersc.gov/research-and-development/knl-cache-mode-performance-coe/ > > A kernel module called zonesort is available to try to help: > https://software.intel.com/en-us/articles/xeon-phi-software > > and this abandoned patch series proposed that for the kernel: > https://lkml.org/lkml/2017/8/23/195 > > Dan's patch series doesn't attempt to ensure buffers won't conflict, but > also reduces the chance that the buffers will. This will make performance > more consistent, albeit slower than "optimal" (which is near impossible > to attain in a general-purpose kernel). That's better than forcing > users to deploy remedies like: > "To eliminate this gradual degradation, we have added a Stream > measurement to the Node Health Check that follows each job; > nodes are rebooted whenever their measured memory bandwidth > falls below 300 GB/s." Robert, thanks for that! Yes, instead of run-to-run variations alternating between almost-never-conflict and nearly-always-conflict, we'll get a random / average distribution of cache conflicts.
