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Re: [libvirt] [PATCH 2/2] cgroup: Enable memory.use_hierarchy of cgroup for domain



On 05/23/2010 07:15 AM, Ryota Ozaki wrote:

[Apologies for the delayed review, and for the fact that you had to ping
us to remind us this had not been visited]

> Through conversation with Kumar L Srikanth-B22348, I found
> that the function of getting memory usage (e.g., virsh dominfo)
> doesn't work for lxc with ns subsystem of cgroup enabled.
> 
> This is because of features of ns and memory subsystems.
> Ns creates child cgroup on every process fork and as a result
> processes in a container are not assigned in a cgroup for
> domain (e.g., libvirt/lxc/test1/). For example, libvirt_lxc
> and init (or somewhat specified in XML) are assigned into
> libvirt/lxc/test1/8839/ and libvirt/lxc/test1/8839/8849/,
> respectively. On the other hand, memory subsystem accounts
> memory usage within a group of processes by default, i.e.,
> it does not take any child (and descendent) groups into
> account. With the two features, virsh dominfo which just
> checks memory usage of a cgroup for domain always returns
> zero because the cgroup has no process.
> 
> Setting memory.use_hierarchy of a group allows to account
> (and limit) memory usage of every descendent groups of the group.

s/descendent/descendant/

> By setting it of a cgroup for domain, we can get proper memory
> usage of lxc with ns subsystem enabled. (To be exact, the
> setting is required only when memory and ns subsystems are
> enabled at the same time, e.g., mount -t cgroup none /cgroup.)
> ---
>  src/util/cgroup.c |   63 +++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 files changed, 59 insertions(+), 4 deletions(-)
> 
> diff --git a/src/util/cgroup.c b/src/util/cgroup.c
> index b8b2eb5..f7d6b41 100644
> --- a/src/util/cgroup.c
> +++ b/src/util/cgroup.c
> @@ -443,7 +443,38 @@ static int virCgroupCpuSetInherit(virCgroupPtr parent, virCgroupPtr group)
>      return rc;
>  }
>  
> -static int virCgroupMakeGroup(virCgroupPtr parent, virCgroupPtr group, int create)
> +static int virCgroupSetMemoryUseHierarchy(virCgroupPtr group)
> +{
> +    int rc = 0;
> +    unsigned long long value;
> +    const char *filename = "memory.use_hierarchy";
> +
> +    rc = virCgroupGetValueU64(group,
> +                              VIR_CGROUP_CONTROLLER_MEMORY,
> +                              filename, &value);
> +    if (rc != 0) {
> +        VIR_ERROR("Failed to read %s/%s (%d)", group->path, filename, rc);

Needs _() translation these days; 'make syntax-check' should have caught
this.

> +        return rc;
> +    }
> +
> +    /* Setting twice causes error, so if already enabled, skip setting */
> +    if (value == 1)
> +        return 0;
> +
> +    VIR_DEBUG("Setting up %s/%s", group->path, filename);

Debug remains untranslated...

> +    rc = virCgroupSetValueU64(group,
> +                              VIR_CGROUP_CONTROLLER_MEMORY,
> +                              filename, 1);
> +
> +    if (rc != 0) {
> +        VIR_ERROR("Failed to set %s/%s (%d)", group->path, filename, rc);

...but another VIR_ERROR that needs translation.

> +    }
> +
> +    return rc;
> +}
> +
> +static int virCgroupMakeGroup(virCgroupPtr parent, virCgroupPtr group,
> +                              int create, int memory_hierarchy)

Based on how this is being used, it seems like you should use
bool/true/false rather than int/0/1 for memory_hierarchy.

>  {
>      int i;
>      int rc = 0;
> @@ -477,6 +508,20 @@ static int virCgroupMakeGroup(virCgroupPtr parent, virCgroupPtr group, int creat
>                      break;
>                  }
>              }
> +            /*
> +             * Note that virCgroupSetMemoryUseHierarchy should always be
> +             * called prior to creating subcgroups and attaching tasks.
> +             */
> +            if (memory_hierarchy &&
> +                group->controllers[VIR_CGROUP_CONTROLLER_MEMORY].mountPoint != NULL &&
> +                (i == VIR_CGROUP_CONTROLLER_MEMORY ||
> +                 STREQ(group->controllers[i].mountPoint, group->controllers[VIR_CGROUP_CONTROLLER_MEMORY].mountPoint))) {
> +                rc = virCgroupSetMemoryUseHierarchy(group);
> +                if (rc != 0) {
> +                    VIR_FREE(path);
> +                    break;
> +                }
> +            }
>          }
>  
>          VIR_FREE(path);
> @@ -553,7 +598,7 @@ static int virCgroupAppRoot(int privileged,
>      if (rc != 0)
>          goto cleanup;
>  
> -    rc = virCgroupMakeGroup(rootgrp, *group, create);
> +    rc = virCgroupMakeGroup(rootgrp, *group, create, 0);
>  

ACK with those nits addressed.  Hopefully a v2 submission won't take as
much time on the review side of things.

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

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