* [PATCH] xen/Kconfig: Correct the NR_CPUS description
@ 2020-12-18 23:38 Andrew Cooper
2020-12-21 8:37 ` Jan Beulich
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Cooper @ 2020-12-18 23:38 UTC (permalink / raw)
To: Xen-devel
Cc: Andrew Cooper, Jan Beulich, Roger Pau Monné,
Wei Liu, Stefano Stabellini, Julien Grall, Volodymyr Babchuk,
hanetzer
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(-)
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.
--
2.11.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] xen/Kconfig: Correct the NR_CPUS description
2020-12-18 23:38 [PATCH] xen/Kconfig: Correct the NR_CPUS description Andrew Cooper
@ 2020-12-21 8:37 ` Jan Beulich
2020-12-21 10:29 ` Andrew Cooper
0 siblings, 1 reply; 3+ messages in thread
From: Jan Beulich @ 2020-12-21 8:37 UTC (permalink / raw)
To: Andrew Cooper
Cc: Roger Pau Monné,
Wei Liu, Stefano Stabellini, Julien Grall, Volodymyr Babchuk,
hanetzer, Xen-devel
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>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] xen/Kconfig: Correct the NR_CPUS description
2020-12-21 8:37 ` Jan Beulich
@ 2020-12-21 10:29 ` Andrew Cooper
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Cooper @ 2020-12-21 10:29 UTC (permalink / raw)
To: Jan Beulich
Cc: Roger Pau Monné,
Wei Liu, Stefano Stabellini, Julien Grall, Volodymyr Babchuk,
hanetzer, Xen-devel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-12-21 10:30 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-12-18 23:38 [PATCH] xen/Kconfig: Correct the NR_CPUS description Andrew Cooper
2020-12-21 8:37 ` Jan Beulich
2020-12-21 10:29 ` Andrew Cooper
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