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Re: [PATCH 1/8] hmat acpi: Don't require initiator value in -numa


From: Brice Goglin
Subject: Re: [PATCH 1/8] hmat acpi: Don't require initiator value in -numa
Date: Mon, 18 Jul 2022 07:43:41 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0


Le 18/07/2022 à 05:17, Liu, Jingqi a écrit :

On 7/11/2022 6:44 PM, Hesham Almatary via wrote:
From: Brice Goglin <Brice.Goglin@inria.fr>

The "Memory Proximity Domain Attributes" structure of the ACPI HMAT
has a "Processor Proximity Domain Valid" flag that is currently
always set because Qemu -numa requires an initiator=X value
when hmat=on. Unsetting this flag allows to create more complex
memory topologies by having multiple best initiators for a single
memory target.

Do you mean the memory-only numa node requires an initiator=X value ?

It would be better if you can explicitly provide cases in the description

for creating more complex memory topologies without initiator=X.


Hello

I wrote this text so I am going to reply. All nodes currently require an initiator= attribute. For CPU-node, that's usually OK. However it forces all nodes to have a best initiator that is exactly one single node. This prevents creating a topology where some memory has for best initiator the sum of 2 nodes for instance. There's an example below in the description. A real-world example would be a Xeon server with SNC enabled: there are 2 DDR per socket, one per SNC, but a single NVDIMM per socket covering both SNC. That NVDIMM node cannot have a single initiator value since its best initiator is both SNC. That's similar to the example below in the description

Brice




Thanks,

Jingqi

This patch allows -numa without initiator=X when hmat=on by keeping
the default value MAX_NODES in numa_state->nodes[i].initiator.
All places reading numa_state->nodes[i].initiator already check
whether it's different from MAX_NODES before using it.

Tested with
qemu-system-x86_64 -accel kvm \
  -machine pc,hmat=on \
  -drive if=pflash,format=raw,file=./OVMF.fd \
  -drive media=disk,format=qcow2,file=efi.qcow2 \
  -smp 4 \
  -m 3G \
  -object memory-backend-ram,size=1G,id=ram0 \
  -object memory-backend-ram,size=1G,id=ram1 \
  -object memory-backend-ram,size=1G,id=ram2 \
  -numa node,nodeid=0,memdev=ram0,cpus=0-1 \
  -numa node,nodeid=1,memdev=ram1,cpus=2-3 \
  -numa node,nodeid=2,memdev=ram2 \
  -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=10 \   -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=10485760 \   -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=20 \   -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=5242880 \   -numa hmat-lb,initiator=0,target=2,hierarchy=memory,data-type=access-latency,latency=30 \   -numa hmat-lb,initiator=0,target=2,hierarchy=memory,data-type=access-bandwidth,bandwidth=1048576 \   -numa hmat-lb,initiator=1,target=0,hierarchy=memory,data-type=access-latency,latency=20 \   -numa hmat-lb,initiator=1,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=5242880 \   -numa hmat-lb,initiator=1,target=1,hierarchy=memory,data-type=access-latency,latency=10 \   -numa hmat-lb,initiator=1,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=10485760 \   -numa hmat-lb,initiator=1,target=2,hierarchy=memory,data-type=access-latency,latency=30 \   -numa hmat-lb,initiator=1,target=2,hierarchy=memory,data-type=access-bandwidth,bandwidth=1048576 which reports NUMA node2 at same distance from both node0 and node1 as seen in lstopo:
Machine (2966MB total) + Package P#0
   NUMANode P#2 (979MB)
   Group0
     NUMANode P#0 (980MB)
     Core P#0 + PU P#0
     Core P#1 + PU P#1
   Group0
     NUMANode P#1 (1007MB)
     Core P#2 + PU P#2
     Core P#3 + PU P#3

Before this patch, we had to add ",initiator=X" to "-numa node,nodeid=2,memdev=ram2".
The lstopo output difference between initiator=1 and no initiator is:
@@ -1,10 +1,10 @@
  Machine (2966MB total) + Package P#0
+  NUMANode P#2 (979MB)
    Group0
      NUMANode P#0 (980MB)
      Core P#0 + PU P#0
      Core P#1 + PU P#1
    Group0
      NUMANode P#1 (1007MB)
-    NUMANode P#2 (979MB)
      Core P#2 + PU P#2
      Core P#3 + PU P#3

Corresponding changes in the HMAT MPDA structure:
@@ -49,10 +49,10 @@
  [078h 0120   2]               Structure Type : 0000 [Memory Proximity Domain Attributes]
  [07Ah 0122   2]                     Reserved : 0000
  [07Ch 0124   4]                       Length : 00000028
-[080h 0128   2]        Flags (decoded below) : 0001
-            Processor Proximity Domain Valid : 1
+[080h 0128   2]        Flags (decoded below) : 0000
+            Processor Proximity Domain Valid : 0
  [082h 0130   2]                    Reserved1 : 0000
-[084h 0132   4] Attached Initiator Proximity Domain : 00000001
+[084h 0132   4] Attached Initiator Proximity Domain : 00000080
  [088h 0136   4]      Memory Proximity Domain : 00000002
  [08Ch 0140   4]                    Reserved2 : 00000000
  [090h 0144   8]                    Reserved3 : 0000000000000000

Final HMAT SLLB structures:
[0A0h 0160   2]               Structure Type : 0001 [System Locality Latency and Bandwidth Information]
[0A2h 0162   2]                     Reserved : 0000
[0A4h 0164   4]                       Length : 00000040
[0A8h 0168   1]        Flags (decoded below) : 00
                             Memory Hierarchy : 0
[0A9h 0169   1]                    Data Type : 00
[0AAh 0170   2]                    Reserved1 : 0000
[0ACh 0172   4] Initiator Proximity Domains # : 00000002
[0B0h 0176   4]   Target Proximity Domains # : 00000003
[0B4h 0180   4]                    Reserved2 : 00000000
[0B8h 0184   8]              Entry Base Unit : 0000000000002710
[0C0h 0192   4] Initiator Proximity Domain List : 00000000
[0C4h 0196   4] Initiator Proximity Domain List : 00000001
[0C8h 0200   4] Target Proximity Domain List : 00000000
[0CCh 0204   4] Target Proximity Domain List : 00000001
[0D0h 0208   4] Target Proximity Domain List : 00000002
[0D4h 0212   2]                        Entry : 0001
[0D6h 0214   2]                        Entry : 0002
[0D8h 0216   2]                        Entry : 0003
[0DAh 0218   2]                        Entry : 0002
[0DCh 0220   2]                        Entry : 0001
[0DEh 0222   2]                        Entry : 0003

[0E0h 0224   2]               Structure Type : 0001 [System Locality Latency and Bandwidth Information]
[0E2h 0226   2]                     Reserved : 0000
[0E4h 0228   4]                       Length : 00000040
[0E8h 0232   1]        Flags (decoded below) : 00
                             Memory Hierarchy : 0
[0E9h 0233   1]                    Data Type : 03
[0EAh 0234   2]                    Reserved1 : 0000
[0ECh 0236   4] Initiator Proximity Domains # : 00000002
[0F0h 0240   4]   Target Proximity Domains # : 00000003
[0F4h 0244   4]                    Reserved2 : 00000000
[0F8h 0248   8]              Entry Base Unit : 0000000000000001
[100h 0256   4] Initiator Proximity Domain List : 00000000
[104h 0260   4] Initiator Proximity Domain List : 00000001
[108h 0264   4] Target Proximity Domain List : 00000000
[10Ch 0268   4] Target Proximity Domain List : 00000001
[110h 0272   4] Target Proximity Domain List : 00000002
[114h 0276   2]                        Entry : 000A
[116h 0278   2]                        Entry : 0005
[118h 0280   2]                        Entry : 0001
[11Ah 0282   2]                        Entry : 0005
[11Ch 0284   2]                        Entry : 000A
[11Eh 0286   2]                        Entry : 0001

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
---
  hw/core/machine.c | 4 +---
  1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index a673302cce..d4d7e77401 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1173,9 +1173,7 @@ static void numa_validate_initiator(NumaState *numa_state)
        for (i = 0; i < numa_state->num_nodes; i++) {
          if (numa_info[i].initiator == MAX_NODES) {
-            error_report("The initiator of NUMA node %d is missing, use " -                         "'-numa node,initiator' option to declare it", i);
-            exit(1);
+            continue;
          }
            if (!numa_info[numa_info[i].initiator].present) {

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