From d45fad47e4506f72eda899ebae8405cc829905d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Edwin=20T=C3=B6r=C3=B6k?= <edwin.torok@cloud.com>
Date: Thu, 22 Aug 2024 16:27:10 +0100
Subject: [PATCH] CP-52709: autotune service

bindir
---
 ocaml/hwtune/dune        |  5 +++++
 ocaml/hwtune/xshwtune.ml | 44 ++++++++++++++++++++++++++++++++++++++++
 scripts/Makefile         |  1 +
 scripts/xshwtune.service | 15 ++++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 ocaml/hwtune/dune
 create mode 100644 ocaml/hwtune/xshwtune.ml
 create mode 100644 scripts/xshwtune.service

diff --git a/ocaml/hwtune/dune b/ocaml/hwtune/dune
new file mode 100644
index 00000000000..37139c593c8
--- /dev/null
+++ b/ocaml/hwtune/dune
@@ -0,0 +1,5 @@
+(executable
+	(public_name xshwtune)
+	(libraries xapi_timeslice unix xapi-log)
+	(package xapi)
+)
diff --git a/ocaml/hwtune/xshwtune.ml b/ocaml/hwtune/xshwtune.ml
new file mode 100644
index 00000000000..a46237442ef
--- /dev/null
+++ b/ocaml/hwtune/xshwtune.ml
@@ -0,0 +1,44 @@
+(* Tunes parameters for the hardware and kernel that we are currently running on. *)
+
+module D = Debug.Make (struct let name = "xshwtune" end)
+
+let () =
+  Debug.log_to_stdout () ;
+  let recommended = Xapi_timeslice.Recommended.measure () in
+  D.debug "Recommended OCaml timeslice: %.6fs" recommended ;
+
+  let itimer_min =
+    Sys.set_signal Sys.sigvtalrm Sys.Signal_ignore ;
+    let _ =
+      Unix.setitimer Unix.ITIMER_VIRTUAL
+        Unix.{it_value= 1e-6; it_interval= 1e-6}
+    in
+    let actual = Unix.getitimer Unix.ITIMER_VIRTUAL in
+    actual.Unix.it_value
+  in
+
+  D.debug "POSIX itimer granularity: %.6fs" itimer_min ;
+  let recommended = Float.max itimer_min recommended in
+
+  (* just in case something goes very wrong, ensure it is not too small or big *)
+  let recommended = recommended |> Float.max 0.001 |> Float.min 0.050 in
+  D.debug "Adjusted timeslice: %.6fs" recommended ;
+
+  (* Use consistent rounding in debug messages and conf file,
+     by converting to string in a single place.
+  *)
+  let recommended = Printf.sprintf "%.3f" recommended in
+
+  D.info "OCaml timeslice: %s" recommended ;
+
+  let write_conf path =
+    Out_channel.with_open_text path @@ fun ch ->
+    Printf.fprintf ch "timeslice=%s" recommended
+  in
+
+  Array.iteri
+    (fun i arg ->
+      if i > 0 then
+        write_conf arg
+    )
+    Sys.argv
diff --git a/scripts/Makefile b/scripts/Makefile
index 503e7838546..64980496000 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -58,6 +58,7 @@ install:
 	$(IDATA) xapi-domains.service $(DESTDIR)/usr/lib/systemd/system/xapi-domains.service
 	$(IDATA) generate-iscsi-iqn.service $(DESTDIR)/usr/lib/systemd/system/generate-iscsi-iqn.service
 	$(IDATA) xapi.service $(DESTDIR)/usr/lib/systemd/system/xapi.service
+	$(IDATA) xshwtune.service $(DESTDIR)/usr/lib/systemd/system/xshwtune.service
 	$(IDATA) attach-static-vdis.service $(DESTDIR)/usr/lib/systemd/system/attach-static-vdis.service
 	$(IDATA) save-boot-info.service $(DESTDIR)/usr/lib/systemd/system/save-boot-info.service
 	$(IDATA) mpathalert.service $(DESTDIR)/usr/lib/systemd/system/mpathalert.service
diff --git a/scripts/xshwtune.service b/scripts/xshwtune.service
new file mode 100644
index 00000000000..c6ad638726c
--- /dev/null
+++ b/scripts/xshwtune.service
@@ -0,0 +1,15 @@
+[Unit]
+Description=Tune system for current hardware and kernel
+Before=xapi.service xenopsd-xc.service
+ConditionPathExists=/etc/xenserver/features.d/ocamltimeslice
+ConditionPathExists=!@ETCDIR@/xenopsd.conf.d/xshwtune.conf
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecCondition=/bin/bash -c '[ "$($</etc/xenserver/features.d/ocamltimeslice)" = "1" ]'
+ExecStartPre=/usr/bin/mkdir -p /etc/xapi.conf.d /etc/xenopsd.conf.d
+ExecStart=/usr/bin/xshwtune @ETCDIR@/xapi.conf.d/xshwtune.conf @ETCDIR@/xenopsd.conf.d/xshwtune.conf
+
+[Install]
+WantedBy=multi-user.target