Bjorn Helgaas [off-list ref] writes:

On Wed, Aug 08, 2018 at 03:44:03PM +0100, Punit Agrawal wrote:

quoted

Bjorn Helgaas [off-list ref] writes:

quoted

On Thu, Aug 2, 2018 at 9:33 AM Lorenzo Pieralisi
[off-list ref] wrote:

quoted

On Wed, Aug 01, 2018 at 02:38:51PM -0500, Jeremy Linton wrote:

Jiang Liu does not work on the kernel anymore so we won't know
anytime soon the reasoning behind commit 965cd0e4a5e5

quoted

On 08/01/2018 12:31 PM, Punit Agrawal wrote:

quoted

Memory for host controller data structures is allocated local to the
node to which the controller is associated with. This has been the
behaviour since support for ACPI was added in
commit 0cb0786bac15 ("ARM64: PCI: Support ACPI-based PCI host controller").

Which was apparently influenced by:

965cd0e4a5e5 x86, PCI, ACPI: Use kmalloc_node() to optimize for performance

Was there an actual use-case behind that change?

I think this fixes the immediate boot problem, but if there is any
perf advantage it seems wise to keep it... Particularly since x86
seems to be doing the node sanitation in pci_acpi_root_get_node().

I am struggling to see the perf advantage of allocating a struct
that the PCI controller will never read/write from a NUMA node that
is local to the PCI controller, happy to be corrected if there is
a sound rationale behind that.

If there is no reason to use kzalloc_node() here, we shouldn't use it.

But we should use it (or not use it) consistently across arches.  I do
not believe there is an arch-specific reason to be different.
Currently, pci_acpi_scan_root() uses kzalloc_node() on x86 and arm64,
but kzalloc() on ia64.  They all ought to be the same.

From my understanding, arm64 use of kzalloc_node() was derived from the
x86 version. Maybe somebody familiar with behaviour on x86 can provide
input here.

If you want to remove use of kzalloc_node(), I'm fine with that as
long as you do it for x86 at the same time (maybe separate patches,
but at least in the same series).

I don't see any evidence in 965cd0e4a5e5 ("x86, PCI, ACPI: Use
kmalloc_node() to optimize for performance") that it actually improves
performance, so I'd be inclined to just use kzalloc().

Thanks for confirming.

I'm happy to add a patch updating x86 use of kzalloc_node() as
well. I'll post something once the merge window closes.

Bjorn