[libvirt] [PATCH v2 02/14] libxl: populate xenstore memory entries at startup, handle dom0_mem

[Marek Marczykowski-Górecki]

libxl uses some xenstore entries for hints in memory management
(especially when starting new domain). This includes dom0 memory limit
and Xen free memory margin, based on current system state. Entries are
created at first function usage, so force such call at daemon startup,
which most likely will be before any domain startup.
Also prevent automatic memory management if dom0_mem= option passed to
xen hypervisor - it is known to be incompatible with autoballoon.

Changes in v2:
 - disable autoballoon when dom0_mem option detected
 - rebase on 1.0.6+

Signed-off-by: Marek Marczykowski-Górecki <marmarek at invisiblethingslab.com>
---
 src/libxl/libxl_conf.h   |  4 ++++
 src/libxl/libxl_driver.c | 36 +++++++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h
index 44ecd41..e8fb9c4 100644
--- a/src/libxl/libxl_conf.h
+++ b/src/libxl/libxl_conf.h
@@ -62,6 +62,10 @@ struct _libxlDriverPrivate {
 
     virPortAllocatorPtr reservedVNCPorts;
 
+    /* should libxl/libvirt take care of getting memory for new domain from
+     * dom0? */
+    bool autoballoon;
+
     size_t nactive;
     virStateInhibitCallback inhibitCallback;
     void *inhibitOpaque;
diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index 3990354..0a0690d 100644
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -29,6 +29,7 @@
 #include <math.h>
 #include <libxl.h>
 #include <fcntl.h>
+#include <regex.h>
 
 #include "internal.h"
 #include "virlog.h"
@@ -963,7 +964,7 @@ libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
     if (libxlBuildDomainConfig(driver, vm->def, &d_config) < 0)
         goto error;
 
-    if (libxlFreeMem(priv, &d_config) < 0) {
+    if (driver->autoballoon && libxlFreeMem(priv, &d_config) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        _("libxenlight failed to get free memory for domain '%s'"),
                        d_config.c_info.name);
@@ -1145,6 +1146,28 @@ libxlStateCleanup(void)
     return 0;
 }
 
+static int auto_autoballoon(libxlDriverPrivatePtr driver)
+{
+    const libxl_version_info *info;
+    regex_t regex;
+    int ret;
+
+    info = libxl_get_version_info(driver->ctx);
+    if (!info)
+        return 1; /* default to on */
+
+    ret = regcomp(&regex,
+            "(^| )dom0_mem=((|min:|max:)[0-9]+[bBkKmMgG]?,?)+($| )",
+            REG_NOSUB | REG_EXTENDED);
+    if (ret)
+        return 1;
+
+    ret = regexec(&regex, info->commandline, 0, NULL, 0);
+    regfree(&regex);
+    return ret == REG_NOMATCH;
+}
+
+
 static int
 libxlStateInitialize(bool privileged,
                      virStateInhibitCallback callback ATTRIBUTE_UNUSED,
@@ -1154,6 +1177,7 @@ libxlStateInitialize(bool privileged,
     char *log_file = NULL;
     virCommandPtr cmd;
     int status, ret = 0;
+    unsigned int free_mem;
     char ebuf[1024];
 
     /* Disable libxl driver if non-root */
@@ -1278,6 +1302,16 @@ libxlStateInitialize(bool privileged,
                                                        NULL)))
         goto error;
 
+    /* This will fill xenstore info about free and dom0 memory if missing,
+     * should be called before starting first domain */
+    if (libxl_get_free_memory(libxl_driver->ctx, &free_mem)) {
+        VIR_ERROR(_("cannot get free memory info"));
+        goto error;
+    }
+
+    /* setup autoballoon */
+    libxl_driver->autoballoon = auto_autoballoon(libxl_driver);
+
     /* Load running domains first. */
     if (virDomainObjListLoadAllConfigs(libxl_driver->domains,
                                        libxl_driver->stateDir,
-- 
1.8.1.4