Re: [libvirt] [PATCH] qemu: add entry for balloon stat stat-disk-caches
On 06/05/2018 03:08 PM, Erik Skultety wrote:
On Tue, Jun 05, 2018 at 01:41:02PM +0200, Tomáš Golembiovský wrote:
> Signed-off-by: Tomáš Golembiovský <tgolembi(a)redhat.com>
> ---
> include/libvirt/libvirt-domain.h | 9 ++++++++-
> src/qemu/qemu_monitor_json.c | 2 ++
> 2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
> index da773b76cb..b96c018a90 100644
> --- a/include/libvirt/libvirt-domain.h
> +++ b/include/libvirt/libvirt-domain.h
> @@ -628,11 +628,18 @@ typedef enum {
> /* Timestamp of the last update of statistics, in seconds. */
> VIR_DOMAIN_MEMORY_STAT_LAST_UPDATE = 9,
>
> + /*
> + * The amount of memory, in bytes, that can be quickly reclaimed without
> + * additional I/O. Typically these pages are used for caching files from
> + * disk.
> + */
> + VIR_DOMAIN_MEMORY_STAT_DISK_CACHES = 10,
> +
> /*
> * The number of statistics supported by this version of the interface.
> * To add new statistics, add them to the enum and increase this value.
> */
> - VIR_DOMAIN_MEMORY_STAT_NR = 10,
> + VIR_DOMAIN_MEMORY_STAT_NR = 11,
this is a public header, this must never change, otherwise you break backwards
compatibility...
Not true. This is meant to work roughly like this:
virDomainMemoryStatStruct stats[VIR_DOMAIN_MEMORY_STAT_NR];
nr_stats = virDomainMemoryStats(dom, stats, VIR_DOMAIN_MEMORY_STAT_NR, 0);
And depending what version you are compiled with you will get different
number of results. Important to say that to maintain backward
compatibility we have a rule that says _NR can only grow and never
shrink. Tomas' patch is actually correct (in this aspect).
View examples:
200a40f94ec9427eb7187d9d5396ad3a3f2925c8
65bf044686c7502ba16f1bee5763fd3e448994fd
Michal