[libvirt] [PATCH v3] libxl: populate xenstore memory entries at startup, handle dom0_mem

[Jim Fehlig]

Marek Marczykowski-Górecki wrote:
> 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.
>
> Signed-off-by: Marek Marczykowski-Górecki <marmarek at invisiblethingslab.com>
> ---
> Changes in v2:
>  - disable autoballoon when dom0_mem option detected
>  - rebase on 1.0.6+
> Changes in v3:
>  - improve comments and error messages
>  - rename auto_autoballoon
>
>  src/libxl/libxl_conf.h   |  4 ++++
>  src/libxl/libxl_driver.c | 37 ++++++++++++++++++++++++++++++++++++-
>  2 files changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h
> index 44ecd41..42bcdbc 100644
> --- a/src/libxl/libxl_conf.h
> +++ b/src/libxl/libxl_conf.h
> @@ -62,6 +62,10 @@ struct _libxlDriverPrivate {
>  
>      virPortAllocatorPtr reservedVNCPorts;
>  
> +    /* Controls automatic ballooning of domain0. If true, get memory for new
> +     * domains from domain0. */
> +    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..89f4f12 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);
> @@ -1146,6 +1147,29 @@ libxlStateCleanup(void)
>  }
>  
>  static int
> +libxlGetAutoballoon(libxlDriverPrivatePtr driver)
>   

I changed this function to return a bool as suggested in v2 and pushed.

Regards,
Jim

> +{
> +    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,
>                       void *opaque ATTRIBUTE_UNUSED)
> @@ -1154,6 +1178,7 @@ 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 +1303,16 @@ 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(_("Unable to configure libxl's memory management parameters"));
> +        goto error;
> +    }
> +
> +    /* setup autoballoon */
> +    libxl_driver->autoballoon = libxlGetAutoballoon(libxl_driver);
> +
>      /* Load running domains first. */
>      if (virDomainObjListLoadAllConfigs(libxl_driver->domains,
>                                         libxl_driver->stateDir,
>