Hi, Michal, Michal Hocko <mhocko@xxxxxxxx> writes: [...] >> >> > Btw. do you have any numbers from running this with some real work >> > workload? >> >> Yes, quite a bit. Do you have a specific scenario in mind? Folks seem >> to come at this in two different ways: >> >> Some want to know how much DRAM they can replace by buying some PMEM. >> They tend to care about how much adding the (cheaper) PMEM slows them >> down versus (expensive) DRAM. They're making a cost-benefit call >> >> Others want to repurpose some PMEM they already have. They want to know >> how much using PMEM in this way will speed them up. They will basically >> take any speedup they can get. >> >> I ask because as a kernel developer with PMEM in my systems, I find the >> "I'll take what I can get" case more personally appealing. But, the >> business folks are much more keen on the "DRAM replacement" use. Do you >> have any thoughts on what you would like to see? > > I was thinking about typical large in memory processing (e.g. in memory > databases) where the hot part of the working set is only a portion and > spilling over to a slower memory can be still benefitial because IO + > data preprocessing on cold data is much slower. We have tested the patchset with the postgresql and pgbench. On a machine with DRAM and PMEM, the kernel with the patchset can improve the score of pgbench up to 22.1% compared with that of the DRAM only + disk case. This comes from the reduced disk read throughput (which reduces up to 70.8%). Best Regards, Huang, Ying
