Store domain %CPU and memory history.

diff --git a/virt-ctrl/vc_connections.ml b/virt-ctrl/vc_connections.ml
index 7e58aee..210c68a 100644 (file)
--- a/virt-ctrl/vc_connections.ml
+++ b/virt-ctrl/vc_connections.ml
@@ -53,18 +53,45 @@ and connection = int (* connection ID *) * (active list * inactive list)
 and active = int (* domain's ID *)
 and inactive = string (* domain's name *)
 
-(* The last "CPU time" seen for a domain, so we can calculate CPU % usage.
- * Hash of (connid, domid) -> cpu_time [int64].
- *)
-let last_cpu_time = Hashtbl.create 13
-let last_time = ref (Unix.gettimeofday ())
-
 (* Store the node_info and hostname for each connection, fetched
  * once just after we connect since these don't normally change.
  * Hash of connid -> (C.node_info, hostname option, uri)
  *)
 let static_conn_info = Hashtbl.create 13
 
+(* Stores the state and history for each domain.
+ * Hash of (connid, domid) -> mutable domhistory structure.
+ * We never delete entries in this hash table, which may be a problem
+ * for very very long-lived instances of virt-ctrl.
+ *)
+type domhistory = {
+  (* for %CPU calculation: *)
+  mutable last_cpu_time : int64;       (* last virDomainInfo->cpuTime *)
+  mutable last_time : float;           (* exact time we measured the above *)
+
+  (* historical data for graphs etc: *)
+  mutable hist_cpu : int array;                (* historical %CPU *)
+  mutable hist_cpu_posn : int;         (* position within array *)
+  mutable hist_mem : int64 array;       (* historical memory (kilobytes) *)
+  mutable hist_mem_posn : int;         (* position within array *)
+}
+
+let domhistory = Hashtbl.create 13
+
+let new_domhistory () = {
+  last_cpu_time = 0L; last_time = 0.;
+  hist_cpu = Array.make 0 0; hist_cpu_posn = 0;
+  hist_mem = Array.make 0 0L; hist_mem_posn = 0;
+}
+
+(* These set limits on the amount of history we collect. *)
+let hist_max = 86400                   (* max history stored, seconds *)
+let hist_rot = 3600                    (* rotation of array when we hit max *)
+
+(* The types of the display columns in the main window.  The interesting
+ * one of the final (int) field which stores the ID of the row, either
+ * connid or domid.
+ *)
 type columns = string GTree.column * string GTree.column * string GTree.column * string GTree.column * string GTree.column * int GTree.column
 
 let debug_repopulate = true
@@ -75,12 +102,6 @@ let debug_repopulate = true
 let repopulate (tree : GTree.view) (model : GTree.tree_store)
     (col_name_id, col_domname, col_status, col_cpu, col_mem, col_id)
     state =
-  let time_passed =
-    let time_now = Unix.gettimeofday () in
-    let time_passed = time_now -. !last_time in
-    last_time := time_now;
-    time_passed in
-
   (* Which connections have been added or removed? *)
   let conns = get_conns () in
   let added, _, removed =
@@ -226,23 +247,79 @@ let repopulate (tree : GTree.view) (model : GTree.tree_store)
                  let memory = sprintf "%Ld K" info.D.memory in
                  model#set ~row ~column:col_mem memory;
 
-                 let ns_now = info.D.cpu_time in (* ns = nanoseconds *)
-                 let ns_prev =
-                   try
-                     let ns = Hashtbl.find last_cpu_time (conn_id, domid) in
-                     if ns > ns_now then 0L else ns (* Rebooted? *)
-                   with Not_found -> 0L in
-                 Hashtbl.replace last_cpu_time (conn_id, domid) ns_now;
-                 let ns_now = Int64.to_float ns_now in
-                 let ns_prev = Int64.to_float ns_prev in
-                 let ns_used = ns_now -. ns_prev in
-                 let ns_available = 1_000_000_000. *. float nr_cpus in
-                 let cpu_percent =
-                   100. *. (ns_used /. ns_available) /. time_passed in
-                 let cpu_percent = sprintf "%.1f %%" cpu_percent in
-                 model#set ~row ~column:col_cpu cpu_percent;
+                 (* Get domhistory.  For a new domain it won't exist, so
+                  * create an empty one.
+                  *)
+                 let dh =
+                   let key = conn_id, domid in
+                   try Hashtbl.find domhistory key
+                   with Not_found ->
+                     let dh = new_domhistory () in
+                     Hashtbl.add domhistory key dh;
+                     dh in
+
+                 (* Measure current time and domain cpuTime as close
+                  * together as possible.
+                  *)
+                 let time_now = Unix.gettimeofday () in
+                 let cpu_now = info.D.cpu_time in
+
+                 let time_prev = dh.last_time in
+                 let cpu_prev =
+                   if dh.last_cpu_time > cpu_now then 0L (* Rebooted? *)
+                   else dh.last_cpu_time in
+
+                 dh.last_time <- time_now;
+                 dh.last_cpu_time <- cpu_now;
 
-               with Libvirt.Virterror _ -> () (* Ignore any transient error *)
+                 let cpu_percent =
+                   if time_prev > 0. then (
+                     let cpu_now = Int64.to_float cpu_now in
+                     let cpu_prev = Int64.to_float cpu_prev in
+                     let cpu_used = cpu_now -. cpu_prev in
+                     let cpu_available = 1_000_000_000. *. float nr_cpus in
+                     let time_passed = time_now -. time_prev in
+
+                     let cpu_percent =
+                       100. *. (cpu_used /. cpu_available) /. time_passed in
+
+                     let cpu_percent_str = sprintf "%.1f %%" cpu_percent in
+                     model#set ~row ~column:col_cpu cpu_percent_str;
+                     int_of_float cpu_percent
+                   ) else -1 in
+
+                 (* Store history. *)
+                 let store arr posn datum =
+                   if posn >= hist_max then (
+                     (* rotate the array *)
+                     Array.blit arr hist_rot arr 0 (hist_max - hist_rot);
+                     let posn = posn - hist_rot in
+                     arr.(posn) <- datum;
+                     (arr, posn+1)
+                   ) else (
+                     let len = Array.length arr in
+                     if posn < len then (
+                       (* normal update *)
+                       arr.(posn) <- datum;
+                       (arr, posn+1)
+                     ) else (
+                       (* extend the array *)
+                       let len' = min (max (2*len) 1) hist_max in
+                       let arr' = Array.make len' datum in
+                       Array.blit arr 0 arr' 0 len;
+                       (arr', posn+1)
+                     )
+                   )
+                 in
+                 let hist_cpu, hist_cpu_posn =
+                   store dh.hist_cpu dh.hist_cpu_posn cpu_percent in
+                 dh.hist_cpu <- hist_cpu; dh.hist_cpu_posn <- hist_cpu_posn;
+                 let hist_mem, hist_mem_posn =
+                   store dh.hist_mem dh.hist_mem_posn info.D.memory in
+                 dh.hist_mem <- hist_mem; dh.hist_mem_posn <- hist_mem_posn
+
+               with
+                 Libvirt.Virterror _ -> () (* Ignore any transient error *)
              )
          ) (model#iter_children (Some parent));