Re: [RFC PATCH v1 0/6] use mm to manage NVDIMM (pmem) zone

On Mon, May 7, 2018 at 11:46 AM, Matthew Wilcox <willy(a)infradead.org&gt; wrote: > On Mon, May 07, 2018 at 10:50:21PM +0800, Huaisheng Ye wrote: >> Traditionally, NVDIMMs are treated by mm(memory management) subsystem as >> DEVICE zone, which is a virtual zone and both its start and end of pfn >> are equal to 0, mm wouldn’t manage NVDIMM directly as DRAM, kernel uses >> corresponding drivers, which locate at \drivers\nvdimm\ and >> \drivers\acpi\nfit and fs, to realize NVDIMM memory alloc and free with >> memory hot plug implementation. > > You probably want to let linux-nvdimm know about this patch set. > Adding to the cc. Yes, thanks for that! > Also, I only received patch 0 and 4. What happened > to 1-3,5 and 6? > >> With current kernel, many mm’s classical features like the buddy >> system, swap mechanism and page cache couldn’t be supported to NVDIMM. >> What we are doing is to expand kernel mm’s capacity to make it to handle >> NVDIMM like DRAM. Furthermore we make mm could treat DRAM and NVDIMM >> separately, that means mm can only put the critical pages to NVDIMM

>> zone, here we created a new zone type as NVM zone. That is to say for >> traditional(or normal) pages which would be stored at DRAM scope like >> Normal, DMA32 and DMA zones. But for the critical pages, which we hope >> them could be recovered from power fail or system crash, we make them >> to be persistent by storing them to NVM zone.

I think adding yet one more mm-zone is the wrong direction. Instead, what we have been considering is a mechanism to allow a device-dax instance to be given back to the kernel as a distinct numa node managed by the VM. It seems it times to dust off those patches.