Messages in this thread | | | Date | Wed, 1 May 2019 13:20:31 +0800 | From | Fengguang Wu <> | Subject | Re: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node |
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On Thu, Apr 18, 2019 at 11:02:27AM +0200, Michal Hocko wrote: >On Wed 17-04-19 13:43:44, Yang Shi wrote: >[...] >> And, I'm wondering whether this optimization is also suitable to general >> NUMA balancing or not. > >If there are convincing numbers then this should be a preferable way to >deal with it. Please note that the number of promotions is not the only >metric to watch. The overal performance/access latency would be another one.
Good question. Shi and me aligned today. Also talked with Mel (but sorry I must missed some points due to poor English listening). It becomes clear that
1) PMEM/DRAM page promotion/demotion is a hard problem to attack. There will and should be multiple approaches for open discussion before settling down. The criteria might be balanced complexity, overheads, performance, etc.
2) We need a lot more data to lay solid foundation for effective discussions. Testing will be a rather time consuming part for contributor. We'll need to work together to create a number of benchmarks that can well exercise the kernel promotion/demotion paths and gather the necessary numbers. By collaborating on a common set of tests, we can not only amortize efforts, but also compare different approaches or compare v1/v2/... of the same approach conveniently.
Ying has already created several LKP test cases for that purpose. Shi and me plan to join the efforts, too.
Thanks, Fengguang
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