numa: introduce --numa-distance

Introduce a new option `--numa-distance SRC,DST=VAL` to define the
distance cost between two NUMA nodes and simulate non-uniform memory
access.

Example usage:

  $ vng -r --cpu 8 -m 4G \
  >     --numa 1G,cpus=0-1 --numa 1G,cpus=2-3 \
  >     --numa 1G,cpus=4-5 --numa 1G,cpus=6-7 \
  >     --numa-distance 0,1=51 --numa-distance 0,2=31 --numa-distance 0,3=41 \
  >     --numa-distance 1,2=21 --numa-distance 1,3=61 \
  >     --numa-distance 2,3=11 -- numactl -H
  available: 4 nodes (0-3)
  node 0 cpus: 0 1
  node 0 size: 1006 MB
  node 0 free: 974 MB
  node 1 cpus: 2 3
  node 1 size: 953 MB
  node 1 free: 919 MB
  node 2 cpus: 4 5
  node 2 size: 943 MB
  node 2 free: 894 MB
  node 3 cpus: 6 7
  node 3 size: 1006 MB
  node 3 free: 965 MB
  node distances:
  node     0    1    2    3
     0:   10   51   31   41
     1:   51   10   21   61
     2:   31   21   10   11
     3:   41   61   11   10

Signed-off-by: Andrea Righi <[email protected]>

README.md

@@ -286,6 +286,37 @@ Examples
      1:  20  10
 ```
 
+ - Run the current kernel creating 4 NUMA nodes of 1GB each and assign
+   different distance costs between the NUMA nodes to simulate non-uniform
+   memory access:
+```
+   $ vng -r --cpu 8 -m 4G \
+   >     --numa 1G,cpus=0-1 --numa 1G,cpus=2-3 \
+   >     --numa 1G,cpus=4-5 --numa 1G,cpus=6-7 \
+   >     --numa-distance 0,1=51 --numa-distance 0,2=31 --numa-distance 0,3=41 \
+   >     --numa-distance 1,2=21 --numa-distance 1,3=61 \
+   >     --numa-distance 2,3=11 -- numactl -H
+   available: 4 nodes (0-3)
+   node 0 cpus: 0 1
+   node 0 size: 1006 MB
+   node 0 free: 974 MB
+   node 1 cpus: 2 3
+   node 1 size: 953 MB
+   node 1 free: 919 MB
+   node 2 cpus: 4 5
+   node 2 size: 943 MB
+   node 2 free: 894 MB
+   node 3 cpus: 6 7
+   node 3 size: 1006 MB
+   node 3 free: 965 MB
+   node distances:
+   node     0    1    2    3
+      0:   10   51   31   41
+      1:   51   10   21   61
+      2:   31   21   10   11
+      3:   41   61   11   10
+```
+
  - Run `glxgears` inside a kernel recompiled in the current directory:
 ```
    $ vng -g -- glxgears

virtme/commands/run.py

@@ -169,6 +169,12 @@ def make_parser() -> argparse.ArgumentParser:
         default=None,
         help="Create NUMA nodes in the guest.",
     )
+    g.add_argument(
+        "--numa-distance",
+        action="append",
+        default=None,
+        help="Define a distance between two NUMA nodes in the guest (src=ID,dst=ID,val=NUM).",
+    )
     g.add_argument(
         "--cpus", action="store", default=None, help="Set guest cpu and qemu -smp flag."
     )
@@ -1042,6 +1048,12 @@ def do_it() -> int:
                 "-numa", f"node,memdev=mem{i}{cpus}"
             ])
 
+    if args.numa_distance:
+        for arg in args.numa_distance:
+            qemuargs.extend([
+                "-numa", f"dist,{arg}"
+            ])
+
     if args.snaps:
         if args.root == "/":
             snapd_state = "/var/lib/snapd/state.json"

virtme_ng/run.py

@@ -339,6 +339,15 @@ def make_parser():
         + "This option implicitly disables the microvm architecture."
     )
 
+    parser.add_argument(
+        "--numa-distance",
+        metavar="SRC,DST=VAL",
+        action="append",
+        help="Set a distance of VAL between NUMA node SRC_NODE and DST_NODE. "
+        + "Use this option multiple times to define multiple distances between NUMA nodes. "
+        + "This option is used only together with --numa."
+    )
+
     parser.add_argument(
         "--balloon",
         action="store_true",
@@ -1084,6 +1093,25 @@ def _get_virtme_numa(self, args):
         else:
             self.virtme_param["numa"] = ""
 
+    def _get_virtme_numa_distance(self, args):
+        if args.numa_distance is not None:
+            if not args.numa:
+                arg_fail("error: --numa-distance can be used only with --numa", show_usage=False)
+            numa_dist_str = ""
+            for arg in args.numa_distance:
+                try:
+                    nodes = arg.split('=')
+                    src, dst = nodes[0].split(',')
+                    val = nodes[1]
+                    numa_dist_str += f" --numa-distance src={src},dst={dst},val={val}"
+                except ValueError:
+                    err_msg = f"error: invalid distance '{arg}', " + \
+                               "NUMA distance string must be in the format SRC,DST=VAL"
+                    arg_fail(err_msg, show_usage=False)
+            self.virtme_param["numa_distance"] = numa_dist_str
+        else:
+            self.virtme_param["numa_distance"] = ""
+
     def _get_virtme_balloon(self, args):
         if args.balloon:
             self.virtme_param["balloon"] = "--balloon"
@@ -1178,6 +1206,7 @@ def run(self, args):
         self._get_virtme_cpus(args)
         self._get_virtme_memory(args)
         self._get_virtme_numa(args)
+        self._get_virtme_numa_distance(args)
         self._get_virtme_balloon(args)
         self._get_virtme_gdb(args)
         self._get_virtme_snaps(args)
@@ -1221,6 +1250,7 @@ def run(self, args):
             + f'{self.virtme_param["cpus"]} '
             + f'{self.virtme_param["memory"]} '
             + f'{self.virtme_param["numa"]} '
+            + f'{self.virtme_param["numa_distance"]} '
             + f'{self.virtme_param["balloon"]} '
             + f'{self.virtme_param["gdb"]} '
             + f'{self.virtme_param["snaps"]} '