On Mon, Oct 22, 2018 at 1:18 PM Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote: > > Persistent memory is cool. But, currently, you have to rewrite > your applications to use it. Wouldn't it be cool if you could > just have it show up in your system like normal RAM and get to > it like a slow blob of memory? Well... have I got the patch > series for you! > > This series adds a new "driver" to which pmem devices can be > attached. Once attached, the memory "owned" by the device is > hot-added to the kernel and managed like any other memory. On > systems with an HMAT (a new ACPI table), each socket (roughly) > will have a separate NUMA node for its persistent memory so > this newly-added memory can be selected by its unique NUMA > node. Could you please elaborate this? I'm supposed you mean the pmem will be a separate NUMA node, right? I would like to try the patches on real hardware, any prerequisite is needed? Thanks, Yang > > This is highly RFC, and I really want the feedback from the > nvdimm/pmem folks about whether this is a viable long-term > perversion of their code and device mode. It's insufficiently > documented and probably not bisectable either. > > Todo: > 1. The device re-binding hacks are ham-fisted at best. We > need a better way of doing this, especially so the kmem > driver does not get in the way of normal pmem devices. > 2. When the device has no proper node, we default it to > NUMA node 0. Is that OK? > 3. We muck with the 'struct resource' code quite a bit. It > definitely needs a once-over from folks more familiar > with it than I. > 4. Is there a better way to do this than starting with a > copy of pmem.c? > > Here's how I set up a system to test this thing: > > 1. Boot qemu with lots of memory: "-m 4096", for instance > 2. Reserve 512MB of physical memory. Reserving a spot a 2GB > physical seems to work: memmap=512M!0x0000000080000000 > This will end up looking like a pmem device at boot. > 3. When booted, convert fsdax device to "device dax": > ndctl create-namespace -fe namespace0.0 -m dax > 4. In the background, the kmem driver will probably bind to the > new device. > 5. Now, online the new memory sections. Perhaps: > > grep ^MemTotal /proc/meminfo > for f in `grep -vl online /sys/devices/system/memory/*/state`; do > echo $f: `cat $f` > echo online > $f > grep ^MemTotal /proc/meminfo > done > > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> > Cc: Dave Jiang <dave.jiang@xxxxxxxxx> > Cc: Ross Zwisler <zwisler@xxxxxxxxxx> > Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx> > Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: linux-nvdimm@xxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: linux-mm@xxxxxxxxx > Cc: Huang Ying <ying.huang@xxxxxxxxx> > Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx> >
