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Re: [libvirt] [PATCH 16/17] vircgroup: Introduce virCgroupGetMemoryStat



On Fri, Aug 10, 2018 at 10:44:39AM +0200, Michal Privoznik wrote:
> On 08/09/2018 03:44 PM, Pavel Hrdina wrote:
> > Signed-off-by: Pavel Hrdina <phrdina redhat com>
> > ---
> >  src/libvirt_private.syms |  1 +
> >  src/util/vircgroup.c     | 88 ++++++++++++++++++++++++++++++++++++++++
> >  src/util/vircgroup.h     |  7 ++++
> >  3 files changed, 96 insertions(+)
> > 
> > diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> > index 59d9bc380e..ee0dca6129 100644
> > --- a/src/libvirt_private.syms
> > +++ b/src/libvirt_private.syms
> > @@ -1532,6 +1532,7 @@ virCgroupGetDomainTotalCpuStats;
> >  virCgroupGetFreezerState;
> >  virCgroupGetMemoryHardLimit;
> >  virCgroupGetMemorySoftLimit;
> > +virCgroupGetMemoryStat;
> >  virCgroupGetMemoryUsage;
> >  virCgroupGetMemSwapHardLimit;
> >  virCgroupGetMemSwapUsage;
> > diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
> > index 37982a9607..b91acd13c7 100644
> > --- a/src/util/vircgroup.c
> > +++ b/src/util/vircgroup.c
> > @@ -2427,6 +2427,94 @@ virCgroupSetMemory(virCgroupPtr group, unsigned long long kb)
> >  }
> >  
> >  
> > +/**
> > + * virCgroupGetMemoryStat:
> > + *
> > + * @group: The cgroup to change memory for
> > + * @cache: page cache memory in KiB
> > + * @activeAnon: anonymous and swap cache memory in KiB
> > + * @inactiveAnon: anonymous and swap cache memory in KiB
> > + * @activeFile: file-backed memory in KiB
> > + * @inactiveFile: file-backed memory in KiB
> > + * @unevictable: memory that cannot be reclaimed KiB
> > + *
> > + * Returns: 0 on success, -1 on error
> > + */
> > +int
> > +virCgroupGetMemoryStat(virCgroupPtr group,
> > +                       unsigned long long *cache,
> > +                       unsigned long long *activeAnon,
> > +                       unsigned long long *inactiveAnon,
> > +                       unsigned long long *activeFile,
> > +                       unsigned long long *inactiveFile,
> > +                       unsigned long long *unevictable)
> > +{
> > +    int ret = -1;
> > +    char *stat = NULL;
> > +    char *line = NULL;
> > +    unsigned long long cacheVal = 0;
> > +    unsigned long long activeAnonVal = 0;
> > +    unsigned long long inactiveAnonVal = 0;
> > +    unsigned long long activeFileVal = 0;
> > +    unsigned long long inactiveFileVal = 0;
> > +    unsigned long long unevictableVal = 0;
> > +
> > +    if (virCgroupGetValueStr(group,
> > +                             VIR_CGROUP_CONTROLLER_MEMORY,
> > +                             "memory.stat",
> > +                             &stat) < 0) {
> > +        return -1;
> > +    }
> > +
> > +    line = stat;
> > +
> > +    while (line) {
> > +        char *newLine = strchr(line, '\n');
> > +        char *valueStr = strchr(line, ' ');
> > +        unsigned long long value;
> > +
> > +        if (newLine)
> > +            *newLine = '\0';
> > +
> > +        if (!valueStr) {
> > +            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> > +                           _("Cannot parse 'memory.stat' cgroup file."));
> > +            goto cleanup;
> > +        }
> > +        *valueStr = '\0';
> > +
> > +        if (virStrToLong_ull(valueStr + 1, NULL, 10, &value) < 0)
> > +            goto cleanup;
> > +
> > +        if (STREQ(line, "cache"))
> > +            cacheVal = value >> 10;
> 
> 
> Can't we assign directly to *cache? Sure, you'd need to initialize it
> before, just like you're initializing cacheVal.

We can do that, some other functions in vircgroup.c are assigning values
directly into the passed parameters, I wanted to play it safe and update
the passed parameters only if everything succeeds.

Pavel

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