On Fri, Aug 2, 2024 at 3:02 PM Alison Schofield <alison.schofield@xxxxxxxxx> wrote: > > ++ nvdimm, linux-cxl, Yu Zhang > > On Wed, Jun 05, 2024 at 10:27:51PM +0000, Sourav Panda wrote: > > Today, we do not have any observability of per-page metadata > > and how much it takes away from the machine capacity. Thus, > > we want to describe the amount of memory that is going towards > > per-page metadata, which can vary depending on build > > configuration, machine architecture, and system use. > > > > This patch adds 2 fields to /proc/vmstat that can used as shown > > below: > > > > Accounting per-page metadata allocated by boot-allocator: > > /proc/vmstat:nr_memmap_boot * PAGE_SIZE > > > > Accounting per-page metadata allocated by buddy-allocator: > > /proc/vmstat:nr_memmap * PAGE_SIZE > > > > Accounting total Perpage metadata allocated on the machine: > > (/proc/vmstat:nr_memmap_boot + > > /proc/vmstat:nr_memmap) * PAGE_SIZE > > > > Utility for userspace: > > > > Observability: Describe the amount of memory overhead that is > > going to per-page metadata on the system at any given time since > > this overhead is not currently observable. > > > > Debugging: Tracking the changes or absolute value in struct pages > > can help detect anomalies as they can be correlated with other > > metrics in the machine (e.g., memtotal, number of huge pages, > > etc). > > > > page_ext overheads: Some kernel features such as page_owner > > page_table_check that use page_ext can be optionally enabled via > > kernel parameters. Having the total per-page metadata information > > helps users precisely measure impact. Furthermore, page-metadata > > metrics will reflect the amount of struct pages reliquished > > (or overhead reduced) when hugetlbfs pages are reserved which > > will vary depending on whether hugetlb vmemmap optimization is > > enabled or not. > > > > For background and results see: > > lore.kernel.org/all/20240220214558.3377482-1-souravpanda@xxxxxxxxxx > > > > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > > Signed-off-by: Sourav Panda <souravpanda@xxxxxxxxxx> > > Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx> > > This patch is leading to Oops in 6.11-rc1 when CONFIG_MEMORY_HOTPLUG > is enabled. Folks hitting it have had success with reverting this patch. > Disabling CONFIG_MEMORY_HOTPLUG is not a long term solution. > > Reported here: > https://lore.kernel.org/linux-cxl/CAHj4cs9Ax1=CoJkgBGP_+sNu6-6=6v=_L-ZBZY0bVLD3wUWZQg@xxxxxxxxxxxxxx/ Thank you for the heads up. Can you please attach a full config file, also was anyone able to reproduce this problem in qemu with emulated nvdimm? Pasha
