| Message ID | 20201218233842.5277-1-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/Kconfig: Correct the NR_CPUS description | expand |
On 19.12.2020 00:38, Andrew Cooper wrote: > The description "physical CPUs" is especially wrong, as it implies the number > of sockets, which tops out at 8 on all but the very biggest servers. > > NR_CPUS is the number of logical entities the scheduler can use. > > Reported-by: hanetzer@startmail.com This wasn't on xen-devel, was it? > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Acked-by: Jan Beulich <jbeulich@suse.com>
On 21/12/2020 08:37, Jan Beulich wrote: > On 19.12.2020 00:38, Andrew Cooper wrote: >> The description "physical CPUs" is especially wrong, as it implies the number >> of sockets, which tops out at 8 on all but the very biggest servers. >> >> NR_CPUS is the number of logical entities the scheduler can use. >> >> Reported-by: hanetzer@startmail.com > This wasn't on xen-devel, was it? No. It was on IRC, hence the rather late patch. > >> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> > Acked-by: Jan Beulich <jbeulich@suse.com> Thanks. ~Andrew
diff --git a/xen/arch/Kconfig b/xen/arch/Kconfig index 1954d1c5c1..d144d4c8d3 100644 --- a/xen/arch/Kconfig +++ b/xen/arch/Kconfig @@ -1,11 +1,17 @@ config NR_CPUS - int "Maximum number of physical CPUs" + int "Maximum number of CPUs" range 1 4095 default "256" if X86 default "8" if ARM && RCAR3 default "4" if ARM && QEMU default "4" if ARM && MPSOC default "128" if ARM - ---help--- - Specifies the maximum number of physical CPUs which Xen will support. + help + Controls the build-time size of various arrays and bitmaps + associated with multiple-cpu management. It is the upper bound of + the number of logical entities the scheduler can run code on. + + For CPU cores which support Simultaneous Multi-Threading or similar + technologies, this the number of logical threads which Xen will + support.
The description "physical CPUs" is especially wrong, as it implies the number of sockets, which tops out at 8 on all but the very biggest servers. NR_CPUS is the number of logical entities the scheduler can use. Reported-by: hanetzer@startmail.com Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> CC: Roger Pau Monné <roger.pau@citrix.com> CC: Wei Liu <wl@xen.org> CC: Stefano Stabellini <sstabellini@kernel.org> CC: Julien Grall <julien@xen.org> CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com> CC: hanetzer@startmail.com --- xen/arch/Kconfig | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)