Re: [Xen-devel] [PATCH v3 2/8] libxl: implement virDomainMemorystats

[Jim Fehlig <jfehlig@xxxxxxxx>]

Joao Martins wrote:
> Introduce support for domainMemoryStats API call, which
> consequently enables the use of `virsh dommemstat` command to
> query for memory statistics of a domain. We support
> the following statistics: balloon info, available and currently
> in use. swap-in, swap-out, major-faults, minor-faults require
> cooperation of the guest and thus currently not supported.
> 
> We build on the data returned from libxl_domain_info and deliver
> it in the virDomainMemoryStat format.
> 
> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> ---
> Changes since v1:
>  - Cleanup properly after error fetching domain stats
>  - Dispose libxl_dominfo after succesfull call to
>  libxl_domain_info()
>  - Bump version to 1.2.22
> ---
>  src/libxl/libxl_driver.c | 70 
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 70 insertions(+)
> 
> diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
> index 50f6e34..f4fc7bc 100644
> --- a/src/libxl/libxl_driver.c
> +++ b/src/libxl/libxl_driver.c
> @@ -4749,6 +4749,75 @@ libxlDomainGetCPUStats(virDomainPtr dom,
>      return ret;
>  }
>  
> +#define LIBXL_SET_MEMSTAT(TAG, VAL) \
> +        if (i < nr_stats) { \
> +            stats[i].tag = TAG; \
> +            stats[i].val = VAL; \
> +            i++; \
> +        }
> +
> +static int
> +libxlDomainMemoryStats(virDomainPtr dom,
> +                       virDomainMemoryStatPtr stats,
> +                       unsigned int nr_stats,
> +                       unsigned int flags)
> +{
> +    libxlDriverPrivatePtr driver = dom->conn->privateData;
> +    libxlDriverConfigPtr cfg = libxlDriverConfigGet(driver);
> +    virDomainObjPtr vm;
> +    libxl_dominfo d_info;
> +    unsigned mem, maxmem;
> +    size_t i = 0;
> +    int ret = -1;
> +
> +    virCheckFlags(0, -1);
> +
> +    if (!(vm = libxlDomObjFromDomain(dom)))
> +        goto cleanup;
> +
> +    if (virDomainMemoryStatsEnsureACL(dom->conn, vm->def) < 0)
> +        goto cleanup;
> +
> +    if (libxlDomainObjBeginJob(driver, vm, LIBXL_JOB_QUERY) < 0)
> +        goto cleanup;
> +
> +    if (!virDomainObjIsActive(vm)) {
> +        virReportError(VIR_ERR_OPERATION_INVALID,
> +                       "%s", _("domain is not running"));
> +        goto endjob;
> +    }
> +
> +    if (libxl_domain_info(cfg->ctx, &d_info, vm->def->id) != 0) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       _("libxl_domain_info failed for domain '%d'"),
> +                       vm->def->id);
> +        goto endjob;
> +    }
> +    mem = d_info.current_memkb;
> +    maxmem = d_info.max_memkb;
> +
> +    LIBXL_SET_MEMSTAT(VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON, maxmem - mem);

Should this just be 'mem'? On a domain with

  <memory unit='KiB'>1048576</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>

I see

# virsh dommemstat test
actual 1024
available 1049600
rss 1048576

The documentation for VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON only says "Current
balloon value (in KB)". I (perhaps incorrectly) interpret that as the amount of
memory currently assigned to the domain.

Also, I wonder if we should provide rss for Xen domains? I'm not sure it makes
much sense since Xen domains are more than just a process running on the host.
AFAIK, rss would always be set to d_info.current_memkb even if a domain was not
actually using all the memory.

Regards,
Jim

> +    LIBXL_SET_MEMSTAT(VIR_DOMAIN_MEMORY_STAT_AVAILABLE, maxmem);
> +    LIBXL_SET_MEMSTAT(VIR_DOMAIN_MEMORY_STAT_RSS, mem);
> +
> +    ret = i;
> +
> +    libxl_dominfo_dispose(&d_info);
> +
> + endjob:
> +    if (!libxlDomainObjEndJob(driver, vm)) {
> +        virObjectUnlock(vm);
> +        vm = NULL;
> +    }
> +
> + cleanup:
> +    if (vm)
> +        virObjectUnlock(vm);
> +    return ret;
> +}
> +
> +#undef LIBXL_SET_MEMSTAT
> +
>  static int
>  libxlConnectDomainEventRegisterAny(virConnectPtr conn, virDomainPtr dom, int 
> eventID,
>                                     virConnectDomainEventGenericCallback 
> callback,
> @@ -5342,6 +5411,7 @@ static virHypervisorDriver libxlHypervisorDriver = {
>  #endif
>      .nodeGetFreeMemory = libxlNodeGetFreeMemory, /* 0.9.0 */
>      .nodeGetCellsFreeMemory = libxlNodeGetCellsFreeMemory, /* 1.1.1 */
> +    .domainMemoryStats = libxlDomainMemoryStats, /* 1.2.22 */
>      .domainGetCPUStats = libxlDomainGetCPUStats, /* 1.2.22 */
>      .connectDomainEventRegister = libxlConnectDomainEventRegister, /* 0.9.0 
> */
>      .connectDomainEventDeregister = libxlConnectDomainEventDeregister, /* 
> 0.9.0 */


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