Re: [Qemu-devel] [PATCH RESEND v8 09/11] numa: Extend the CLI to provide memory latency and bandwidth information

[Daniel Black <daniel@linux.ibm.com>]

Liu Jingqi, Tao Xu,

Apologies to the late response on a patch on what is already a v8 patch.

The specification of latency and bandwidth is very much following the
ACPI specification.

For a qemu interface I think this should be in more human measurements
(time for latency and a bandwidth rate for the bandwidth).

e.g rather than
 -object memory-backend-ram,size=64M,id=m0
 -object memory-backend-ram,size=64M,id=m1geosync
 -numa node,nodeid=0,memdev=m0
 -numa node,nodeid=1,memdev=m1geosync,initiator=0
 -numa cpu,node-id=0,socket-id=0
 -numa cpu,node-id=0,socket-id=1
 -numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,base-lat=1000,latency=5
 -numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,base-bw=20,bandwidth=5
 -numa
hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,base-lat=100,latency=10
 -numa
 hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,base-bw=20,bandwidth=10


Suggest a form like:

 -numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=NUM[fpnm[s]]
 -numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=NUM[KMGP][Bb[ps]]

So:

 -numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5ns
 -numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=5Gb


So this would remove the base-[lt,bw] settings and compute those internally in qemu based on latency/bandwidth specified with real units.

Also note the linux kernel HMAT latency display doesn't match up with the parameters passed in this patch series. Not sure which is at fault.

Test and results:

x86_64-softmmu/qemu-system-x86_64 -machine pc -nographic   -smp
2,sockets=2 -m 128M,slots=2,maxmem=1G
-kernel /home/dan/repos/linux/vmlinux  -append "console=ttyS0"
-object memory-backend-ram,size=64M,id=m0 -object
memory-backend-ram,size=64M,id=m1geosync -numa node,nodeid=0,memdev=m0
-numa node,nodeid=1,memdev=m1geosync,initiator=0 -numa
cpu,node-id=0,socket-id=0 -numa cpu,node-id=0,socket-id=1 -numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,base-lat=1000,latency=5
-numa
hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,base-bw=20,bandwidth=5
-numa
hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,base-lat=100,latency=10
-numa
hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,base-bw=20,bandwidth=10

The Booting from ROM..[    0.000000] Linux version 5.3.0-rc2+
(dan@volution) (gcc version 9.1.1 20190503 (Red Hat 9.1.1-1) (GCC)) #21
SMP Tue Aug 6 17:15:49 AEST 2019


[    0.419303] HMAT: Memory Flags:0001 Processor Domain:0 Memory Domain:0
[    0.419648] HMAT: Memory Flags:0001 Processor Domain:0 Memory Domain:1
[    0.419956] HMAT: Locality: Flags:00 Type:Access Latency Initiator Domains:1 Target Domains:2 Base:1000
[    0.420527]   Initiator-Target[0-0]:5 nsec
[    0.420791]   Initiator-Target[0-1]:10 nsec
[    0.421068] HMAT: Locality: Flags:00 Type:Access Bandwidth Initiator Domains:1 Target Domains:2 Base:20
[    0.421447]   Initiator-Target[0-0]:100 MB/s
[    0.421635]   Initiator-Target[0-1]:200 MB/s