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Re: [libvirt] [PATCH] memtune: Let virsh know the unlimited value for memory tunables



On 01/10/2011 10:18 PM, Nikunj A. Dadhania wrote:
> Display unlimited when the memory cgroup settings says so. Unlimited is
> represented by INT64_MAX in memory cgroup.
> 
> Signed-off-by: Nikunj A. Dadhania <nikunj linux vnet ibm com>
> Reported-by: Justin Clift <jclift redhat com>
> ---
>  include/libvirt/libvirt.h.in |    1 +
>  src/lxc/lxc_driver.c         |    2 +-
>  src/qemu/qemu_driver.c       |    2 +-
>  src/util/cgroup.c            |   27 +++++++++++++++++++++------
>  src/util/cgroup.h            |    6 +++---
>  tools/virsh.c                |    9 +++++++--
>  6 files changed, 34 insertions(+), 13 deletions(-)
> 
> diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
> index 3c6a54a..cb53f6b 100644
> --- a/include/libvirt/libvirt.h.in
> +++ b/include/libvirt/libvirt.h.in
> @@ -696,6 +696,7 @@ typedef enum {
>   */
>  
>  #define VIR_DOMAIN_MEMORY_FIELD_LENGTH 80
> +#define VIR_DOMAIN_MEMORY_PARAM_UNLIMITED (UINT64_MAX)

() aren't strictly necessary here, but don't hurt, either.

> @@ -907,7 +907,7 @@ int virCgroupSetMemoryHardLimit(virCgroupPtr group, unsigned long kb)
>   *
>   * Returns: 0 on success
>   */
> -int virCgroupGetMemoryHardLimit(virCgroupPtr group, unsigned long *kb)
> +int virCgroupGetMemoryHardLimit(virCgroupPtr group, unsigned long long *kb)

So why is Get changed to ull, but Set remains with just unsigned long?
This patch is still incomplete.  I think you need to touch both
functions, and also virCgroupSetMemory.  Also, in virCgroupSetMemory,
you need to check for overflow, and fail if someone requests an
impossible amount of kb.

>  {
>      long long unsigned int limit_in_bytes;
>      int ret;
> @@ -915,7 +915,12 @@ int virCgroupGetMemoryHardLimit(virCgroupPtr group, unsigned long *kb)
>                                 VIR_CGROUP_CONTROLLER_MEMORY,
>                                 "memory.limit_in_bytes", &limit_in_bytes);
>      if (ret == 0)
> -        *kb = (unsigned long) limit_in_bytes >> 10;
> +    {
> +        if (limit_in_bytes != INT64_MAX)
> +            *kb = (unsigned long long) limit_in_bytes >> 10;

This cast is not necessary, since limit_in_bytes is already ull.

-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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