Mel Gorman <mgorman@xxxxxxx> writes: > On Tue, Jun 25, 2019 at 09:23:22PM +0800, huang ying wrote: >> On Mon, Jun 24, 2019 at 10:25 PM Mel Gorman <mgorman@xxxxxxx> wrote: >> > >> > On Mon, Jun 24, 2019 at 10:56:04AM +0800, Huang Ying wrote: >> > > The autonuma scan period should be increased (scanning is slowed down) >> > > if the majority of the page accesses are shared with other processes. >> > > But in current code, the scan period will be decreased (scanning is >> > > speeded up) in that situation. >> > > >> > > This patch fixes the code. And this has been tested via tracing the >> > > scan period changing and /proc/vmstat numa_pte_updates counter when >> > > running a multi-threaded memory accessing program (most memory >> > > areas are accessed by multiple threads). >> > > >> > >> > The patch somewhat flips the logic on whether shared or private is >> > considered and it's not immediately obvious why that was required. That >> > aside, other than the impact on numa_pte_updates, what actual >> > performance difference was measured and on on what workloads? >> >> The original scanning period updating logic doesn't match the original >> patch description and comments. I think the original patch >> description and comments make more sense. So I fix the code logic to >> make it match the original patch description and comments. >> >> If my understanding to the original code logic and the original patch >> description and comments were correct, do you think the original patch >> description and comments are wrong so we need to fix the comments >> instead? Or you think we should prove whether the original patch >> description and comments are correct? >> > > I'm about to get knocked offline so cannot answer properly. The code may > indeed be wrong and I have observed higher than expected NUMA scanning > behaviour than expected although not enough to cause problems. A comment > fix is fine but if you're changing the scanning behaviour, it should be > backed up with data justifying that the change both reduces the observed > scanning and that it has no adverse performance implications. Got it! Thanks for comments! As for performance testing, do you have some candidate workloads? Best Regards, Huang, Ying
