[Xen-devel] [RFC PATCH 2/3] xl/create: warn if the 'vcpu' parameter exceeds host physical CPUs.

[Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>]

It can be a performance disadvantage to allocate more vCPUs
for a guest that there are physical CPUs. If the guest config
has such setup warn the user. The warning can be silenced by
the usage of '--ignore-warn' (-i) parameter.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 docs/man/xl.pod.1         |    6 ++++++
 tools/libxl/xl_cmdimpl.c  |   21 ++++++++++++++++++---
 tools/libxl/xl_cmdtable.c |    6 ++++--
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/docs/man/xl.pod.1 b/docs/man/xl.pod.1
index e09d330..2ebeb6c 100644
--- a/docs/man/xl.pod.1
+++ b/docs/man/xl.pod.1
@@ -147,6 +147,10 @@ It is possible to pass I<key=value> pairs on the command 
line to provide
 options as if they were written in the configuration file; these override
 whatever is in the I<configfile>.
 
+=item B<-i>, B<--ignore-warn>
+
+Silence warnings.
+
 =back
 
 B<EXAMPLES>
@@ -496,7 +500,9 @@ Attach to domain's VNC server, forking a vncviewer process.
 
 Pass VNC password to vncviewer via stdin.
 
+=item B<-i>, B<--ignore-warn>
 
+Silence warnings.
 
 =back
 
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 3d23fb4..b83676c 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -132,6 +132,7 @@ struct domain_create {
     int vnc;
     int vncautopass;
     int console_autoconnect;
+    int ignore_warn;
     const char *config_file;
     const char *extra_config; /* extra config string */
     const char *restore_file;
@@ -657,8 +658,14 @@ static void parse_config_data(const char *config_source,
         b_info->sched_params.extratime = l;
 
     if (!xlu_cfg_get_long (config, "vcpus", &l, 0)) {
+        unsigned int host_cpu = libxl_get_max_cpus(ctx);
         b_info->max_vcpus = l;
 
+        if (l > host_cpu && dom_info && !dom_info->ignore_warn)
+         fprintf(stderr, "WARNING: You are overcommmitting! You have %d " \
+                 "physical CPUs and want %d vCPUs!\n", host_cpu,
+                 b_info->max_vcpus);
+
         if (libxl_cpu_bitmap_alloc(ctx, &b_info->avail_vcpus, l)) {
             fprintf(stderr, "Unable to allocate cpumap\n");
             exit(1);
@@ -3741,11 +3748,13 @@ int main_restore(int argc, char **argv)
     const char *config_file = NULL;
     struct domain_create dom_info;
     int paused = 0, debug = 0, daemonize = 1, monitor = 1,
-        console_autoconnect = 0, vnc = 0, vncautopass = 0;
+        console_autoconnect = 0, vnc = 0, vncautopass = 0,
+        ignore_warn = 0;
     int opt, rc;
     static struct option opts[] = {
         {"vncviewer", 0, 0, 'V'},
         {"vncviewer-autopass", 0, 0, 'A'},
+        {"ignore-warn", 0, 0, 'i'},
         COMMON_LONG_OPTS,
         {0, 0, 0, 0}
     };
@@ -3773,6 +3782,8 @@ int main_restore(int argc, char **argv)
     case 'A':
         vnc = vncautopass = 1;
         break;
+    case 'i':
+        ignore_warn = 1;
     }
 
     if (argc-optind == 1) {
@@ -3796,7 +3807,7 @@ int main_restore(int argc, char **argv)
     dom_info.vnc = vnc;
     dom_info.vncautopass = vncautopass;
     dom_info.console_autoconnect = console_autoconnect;
-
+    dom_info.ignore_warn = ignore_warn;
     rc = create_domain(&dom_info);
     if (rc < 0)
         return -rc;
@@ -4139,7 +4150,7 @@ int main_create(int argc, char **argv)
     char extra_config[1024];
     struct domain_create dom_info;
     int paused = 0, debug = 0, daemonize = 1, console_autoconnect = 0,
-        quiet = 0, monitor = 1, vnc = 0, vncautopass = 0;
+        quiet = 0, monitor = 1, vnc = 0, vncautopass = 0, ignore_warn = 0;
     int opt, rc;
     static struct option opts[] = {
         {"dryrun", 0, 0, 'n'},
@@ -4147,6 +4158,7 @@ int main_create(int argc, char **argv)
         {"defconfig", 1, 0, 'f'},
         {"vncviewer", 0, 0, 'V'},
         {"vncviewer-autopass", 0, 0, 'A'},
+        {"ignore-warn", 0, 0, 'i'},
         COMMON_LONG_OPTS,
         {0, 0, 0, 0}
     };
@@ -4188,6 +4200,8 @@ int main_create(int argc, char **argv)
     case 'A':
         vnc = vncautopass = 1;
         break;
+    case 'i':
+        ignore_warn = 1;
     }
 
     extra_config[0] = '\0';
@@ -4216,6 +4230,7 @@ int main_create(int argc, char **argv)
     dom_info.vnc = vnc;
     dom_info.vncautopass = vncautopass;
     dom_info.console_autoconnect = console_autoconnect;
+    dom_info.ignore_warn = ignore_warn;
 
     rc = create_domain(&dom_info);
     if (rc < 0)
diff --git a/tools/libxl/xl_cmdtable.c b/tools/libxl/xl_cmdtable.c
index 8a98c6a..6fc8932 100644
--- a/tools/libxl/xl_cmdtable.c
+++ b/tools/libxl/xl_cmdtable.c
@@ -33,7 +33,8 @@ struct cmd_spec cmd_table[] = {
       "-e                      Do not wait in the background for the death of 
the domain.\n"
       "-V, --vncviewer         Connect to the VNC display after the domain is 
created.\n"
       "-A, --vncviewer-autopass\n"
-      "                        Pass VNC password to viewer via stdin."
+      "                        Pass VNC password to viewer via stdin.\n"
+      "-i, --ignore-warn       Silence the warnings.",
     },
     { "config-update",
       &main_config_update, 1, 1,
@@ -172,7 +173,8 @@ struct cmd_spec cmd_table[] = {
       "-e                       Do not wait in the background for the death of 
the domain.\n"
       "-d                       Enable debug messages.\n"
       "-V, --vncviewer          Connect to the VNC display after the domain is 
created.\n"
-      "-A, --vncviewer-autopass Pass VNC password to viewer via stdin."
+      "-A, --vncviewer-autopass Pass VNC password to viewer via stdin.\n"
+      "-i, --ignore-warn        Silence warnings.",
     },
     { "migrate-receive",
       &main_migrate_receive, 0, 1,
-- 
1.7.7.6


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