[PATCH v3 2/2] tools/xenstore: set open file descriptor limit for xenstored

[Juergen Gross <jgross@xxxxxxxx>]

Add a configuration item for the maximum number of domains xenstored
should support and set the limit of open file descriptors accordingly.

For HVM domains there are up to 5 socket connections per domain (2 by
the xl daemon process, and 3 by qemu). So set the ulimit for xenstored
to 5 * XENSTORED_MAX_DOMAINS + 100 (the "+ 100" is for some headroom,
like logging, event channel device, etc.).

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- set ulimit form launch script (Julien Grall)
- split off from original patch (Julien Grall)
---
 tools/hotplug/Linux/init.d/sysconfig.xencommons.in | 7 +++++++
 tools/hotplug/Linux/launch-xenstore.in             | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/tools/hotplug/Linux/init.d/sysconfig.xencommons.in 
b/tools/hotplug/Linux/init.d/sysconfig.xencommons.in
index 5ad4fe0818..2b682415f4 100644
--- a/tools/hotplug/Linux/init.d/sysconfig.xencommons.in
+++ b/tools/hotplug/Linux/init.d/sysconfig.xencommons.in
@@ -32,6 +32,13 @@
 # Changing this requires a reboot to take effect.
 #XENSTORED=@XENSTORED@
 
+## Type: integer
+## Default: 32768
+#
+# Select maximum number of domains supported by xenstored.
+# Only evaluated if XENSTORETYPE is "daemon".
+#XENSTORED_MAX_N_DOMAINS=32768
+
 ## Type: string
 ## Default: ""
 #
diff --git a/tools/hotplug/Linux/launch-xenstore.in 
b/tools/hotplug/Linux/launch-xenstore.in
index 1747c96065..3f8b33dd32 100644
--- a/tools/hotplug/Linux/launch-xenstore.in
+++ b/tools/hotplug/Linux/launch-xenstore.in
@@ -54,6 +54,7 @@ test -f @CONFIG_DIR@/@CONFIG_LEAF_DIR@/xencommons && . 
@CONFIG_DIR@/@CONFIG_LEAF
 
 [ "$XENSTORETYPE" = "daemon" ] && {
        [ -z "$XENSTORED_TRACE" ] || XENSTORED_ARGS="$XENSTORED_ARGS -T 
@XEN_LOG_DIR@/xenstored-trace.log"
+       [ -z "$XENSTORED_MAX_N_DOMAINS" ] && XENSTORED_MAX_N_DOMAINS=32768
        [ -z "$XENSTORED" ] && XENSTORED=@XENSTORED@
        [ -x "$XENSTORED" ] || {
                echo "No xenstored found"
@@ -63,6 +64,7 @@ test -f @CONFIG_DIR@/@CONFIG_LEAF_DIR@/xencommons && . 
@CONFIG_DIR@/@CONFIG_LEAF
        XS_OOM_SCORE=-$(($XENSTORED_OOM_MEM_THRESHOLD * 10))
 
        rm -f @XEN_RUN_DIR@/xenstored.pid
+       N_FILES=$(($XENSTORED_MAX_N_DOMAINS * 5 + 100))
 
        echo -n Starting $XENSTORED...
        $XENSTORED --pid-file @XEN_RUN_DIR@/xenstored.pid $XENSTORED_ARGS
@@ -70,6 +72,7 @@ test -f @CONFIG_DIR@/@CONFIG_LEAF_DIR@/xencommons && . 
@CONFIG_DIR@/@CONFIG_LEAF
        systemd-notify --booted 2>/dev/null || timeout_xenstore $XENSTORED || 
exit 1
        XS_PID=`cat @XEN_RUN_DIR@/xenstored.pid`
        echo $XS_OOM_SCORE >/proc/$XS_PID/oom_score_adj
+       prlimit --pid $XS_PID --nofile=$N_FILES
 
        exit 0
 }
-- 
2.26.2