On Thu, Feb 11, 2021 at 2:19 AM Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > > On Wed, 10 Feb 2021 18:17:25 +0000 > Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > > > On Tue, 9 Feb 2021 16:02:54 -0800 > > Ben Widawsky <ben.widawsky@xxxxxxxxx> wrote: > > > > > From: Dan Williams <dan.j.williams@xxxxxxxxx> > > > > > > Create the /sys/bus/cxl hierarchy to enumerate: > > > > > > * Memory Devices (per-endpoint control devices) > > > > > > * Memory Address Space Devices (platform address ranges with > > > interleaving, performance, and persistence attributes) > > > > > > * Memory Regions (active provisioned memory from an address space device > > > that is in use as System RAM or delegated to libnvdimm as Persistent > > > Memory regions). > > > > > > For now, only the per-endpoint control devices are registered on the > > > 'cxl' bus. However, going forward it will provide a mechanism to > > > coordinate cross-device interleave. > > > > > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > > > One stray header, and a request for a tiny bit of reordering to > > make it easier to chase through creation and destruction. > > > > Either way with the header move to earlier patch I'm fine with this one. > > > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > Actually thinking more on this, what is the justification for the > complexity + overhead of a percpu_refcount vs a refcount A typical refcount does not have the block and drain semantics of a percpu_ref. I'm planning to circle back and make this a first class facility of the cdev interface borrowing the debugfs approach [1], but for now percpu_ref fits the bill locally. > I don't think this is a high enough performance path for it to matter. > Perhaps I'm missing a usecase where it does? It's less about percpu_ref performance and more about the percpu_ref_tryget_live() facility. [1]: http://lore.kernel.org/r/CAPcyv4jEYPsyh0bhbtKGRbK3bgp=_+=2rjx4X0gLi5-25VvDyg@xxxxxxxxxxxxxx
