CA-422187: more accurate claims and debug messages

We noticed that xenguest releases 32 unused pages from the domain's claim.
These are from the low 1MiB video range, so avoid requesting it.

Also always print memory free statistics when `wait_xen_free_mem` is called.
Turns out `scrub_pages` is always 0, since this never got implemented in Xen
(it is hardcoded to 0).

Signed-off-by: Edwin Török <[email protected]>

Author: edwintorok

ocaml/xenopsd/xc/domain.ml

@@ -244,7 +244,10 @@ let wait_xen_free_mem ~xc ?(maximum_wait_time_seconds = 64) required_memory_kib
     in
     (* At exponentially increasing intervals, write  *)
     (* a debug message saying how long we've waited: *)
-    if is_power_of_2 accumulated_wait_time_seconds then
+    if
+      accumulated_wait_time_seconds = 0
+      || is_power_of_2 accumulated_wait_time_seconds
+    then
       debug
         "Waited %i second(s) for memory to become available: %Ld KiB free, %Ld \
          KiB scrub, %Ld KiB required"
@@ -1000,7 +1003,7 @@ let numa_placement domid ~vcpus ~cores ~memory affinity =
               __FUNCTION__ domid ;
             None
       in
-      let nr_pages = Int64.div memory 4096L |> Int64.to_int in
+      let nr_pages = (Int64.div memory 4096L |> Int64.to_int) - 32 in
       try
         D.debug "NUMAClaim domid %d: local claim on node %d: %d pages" domid
           node nr_pages ;
@@ -1129,7 +1132,9 @@ let build_pre ~xc ~xs ~vcpus ~memory ~hard_affinity domid =
                      A failure here is a hard failure: we'd fail allocating
                      memory later anyway
                   *)
-                  let nr_pages = Int64.div memory 4096L |> Int64.to_int in
+                  let nr_pages =
+                    (Int64.div memory 4096L |> Int64.to_int) - 32
+                  in
                   let xcext = Xenctrlext.get_handle () in
                   D.debug "NUMAClaim domid %d: global claim: %d pages" domid
                     nr_pages ;