Messages in this thread | | | Subject | Re: [RFC] Memory Tiering | From | David Hildenbrand <> | Date | Thu, 17 Oct 2019 10:07:07 +0200 |
| |
On 16.10.19 22:05, Dave Hansen wrote: > The memory hierarchy is getting more complicated and the kernel is > playing an increasing role in managing the different tiers. A few > different groups of folks described "migration" optimizations they were > doing in this area at LSF/MM earlier this year. One of the questions > folks asked was why autonuma wasn't being used. > > At Intel, the primary new tier that we're looking at is persistent > memory (PMEM). We'd like to be able to use "persistent memory" > *without* using its persistence properties, treating it as slightly > slower DRAM. Keith Busch has some patches to use NUMA migration to > automatically migrate DRAM->PMEM instead of discarding it near the end > of the reclaim process. Huang Ying has some patches which use a > modified autonuma to migrate frequently-used data *back* from PMEM->DRAM.
Very interesting topic. I heard similar demand from HPC folks (especially involving other memory types ("tiers")). There, I think you often want to let the application manage that. But of course, for many applications an automatic management might already be beneficial.
Am I correct that you are using PMEM in this area along with ZONE_DEVICE and not by giving PMEM to the buddy (add_memory())?
> > We've tried to do this all generically so that it is not tied to > persistent memory and can be applied to any memory types in lots of > topologies. > > We've been running this code in various forms for the past few months, > comparing it to pure DRAM and hardware-based caching. The initial > results are encouraging and we thought others might want to take a look > at the code or run their own experiments. We're expecting to post the > individual patches soon. But, until then, the code is available here: > > https://git.kernel.org/pub/scm/linux/kernel/git/vishal/tiering.git > > and is tagged with "tiering-0.2", aka. d8e31e81b1dca9. > > Note that internally folks have been calling this "hmem" which is > terribly easy to confuse with the existing hmm. There are still some > "hmem"'s in the tree, but I don't expect them to live much longer. >
--
Thanks,
David / dhildenb
| |