CPU strides provide means to effectively bind guests to certain specific
phsyical cores by overallocating virtual CPUs (hardware threads) such
that the sum of virtual CPUs and strides yields an integer multiple of
the CPU dependent threads-per-core factor, e.g. on T2 based machines
each CPU has 8 cores and each core has 8 threads. this makes for n times
virtual CPUs to be managed in ldom.conf(5).
Diff below slightly extends the given example and tries to further
clarify what strides do. The example should match a T5120 machine for
example which features 1 T2+ CPU.
It hopefully makes it clearer how "vcpu"s correspond to hardware threads
not physical CPU cores.
Feedback? OK?
Index: ldom.conf.5
===================================================================
RCS file: /cvs/src/usr.sbin/ldomctl/ldom.conf.5,v
retrieving revision 1.9
diff -u -p -r1.9 ldom.conf.5
--- ldom.conf.5 3 Dec 2019 21:07:03 -0000 1.9
+++ ldom.conf.5 4 Jan 2020 20:17:38 -0000
@@ -78,11 +78,11 @@ Configure the MTU of the interface.
.El
.El
.Sh EXAMPLES
-Define a domain with 12 virtual cores, 4GB memory, two file based virtual disks
-and one virtual network interface:
+Define a domain with 12 virtual cores and 4 additionally allocated cores,
+4GB memory, two file based virtual disks and one virtual network interface:
.Bd -literal -offset indent
domain "puffy" {
- vcpu 12
+ vcpu 12:4
memory 4G
vdisk "/home/puffy/vdisk0"
vdisk "/home/puffy/vdisk1"
@@ -101,8 +101,10 @@ domain "salmah" {
}
.Ed
.Pp
-On a machine with 32 cores and 64GB physical memory, this leaves 12 cores and
-58GB memory to the primary domain.
+On a machine with 1 CPU comprising 8 cores with 8 threads each and 64GB
physical
+memory, this leaves 40 cores and 58GB memory to the primary domain.
+.Dq puffy
+will be assigned 16 cores of which 4 are not being used.
.Sh SEE ALSO
.Xr eeprom 8 ,
.Xr ldomctl 8 ,
