On Thu, 11 Feb 2021 12:40:45 -0800 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > 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 Thanks for the reference. Definitely a nasty corner to clean up so I'll keep an eye open for a new version of that series. Jonathan
