[libvirt] [PATCH v3 1/1] qemu: Add entry for balloon stat stat-disk-caches

[Tomáš Golembiovský]

QEMU commit bf1e7140e adds reporting of new balloon statistic to QEMU
2.12. Value represents the amount of memory that can be quickly
reclaimed without additional I/O. Let's add that too.

Signed-off-by: Tomáš Golembiovský <tgolembi at redhat.com>
---
 include/libvirt/libvirt-domain.h | 9 ++++++++-
 src/libvirt-domain.c             | 3 +++
 src/qemu/qemu_driver.c           | 1 +
 src/qemu/qemu_monitor_json.c     | 2 ++
 tools/virsh-domain-monitor.c     | 2 ++
 tools/virsh.pod                  | 5 +++++
 6 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
index 796f2e1408..fdd2d6b8ea 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, that can be quickly reclaimed without
+     * additional I/O (in kB). 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,
 
 # ifdef VIR_ENUM_SENTINELS
     VIR_DOMAIN_MEMORY_STAT_LAST = VIR_DOMAIN_MEMORY_STAT_NR
diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
index c71f2e6877..ef39361c95 100644
--- a/src/libvirt-domain.c
+++ b/src/libvirt-domain.c
@@ -5732,6 +5732,9 @@ virDomainGetInterfaceParameters(virDomainPtr domain,
  *     Current balloon value (in kb).
  * VIR_DOMAIN_MEMORY_STAT_LAST_UPDATE
  *     Timestamp of the last statistic
+ * VIR_DOMAIN_MEMORY_STAT_DISK_CACHES
+ *     Memory that can be reclaimed without additional I/O, typically disk
+ *     caches (in kb).
  *
  * Returns: The number of stats provided or -1 in case of failure.
  */
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 825b2b27e6..f88fb44373 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -19795,6 +19795,7 @@ qemuDomainGetStatsBalloon(virQEMUDriverPtr driver,
         STORE_MEM_RECORD(RSS, "rss")
         STORE_MEM_RECORD(LAST_UPDATE, "last-update")
         STORE_MEM_RECORD(USABLE, "usable")
+        STORE_MEM_RECORD(DISK_CACHES, "disk_caches")
     }
 
 #undef STORE_MEM_RECORD
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index 3e90279b71..9d161fe6f4 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -2071,6 +2071,8 @@ int qemuMonitorJSONGetMemoryStats(qemuMonitorPtr mon,
                       VIR_DOMAIN_MEMORY_STAT_USABLE, 1024);
     GET_BALLOON_STATS(data, "last-update",
                       VIR_DOMAIN_MEMORY_STAT_LAST_UPDATE, 1);
+    GET_BALLOON_STATS(statsdata, "stat-disk-caches",
+                      VIR_DOMAIN_MEMORY_STAT_DISK_CACHES, 1024);
     ret = got;
  cleanup:
     virJSONValueFree(cmd);
diff --git a/tools/virsh-domain-monitor.c b/tools/virsh-domain-monitor.c
index 87660ee674..b9b4f9739b 100644
--- a/tools/virsh-domain-monitor.c
+++ b/tools/virsh-domain-monitor.c
@@ -364,6 +364,8 @@ cmdDomMemStat(vshControl *ctl, const vshCmd *cmd)
             vshPrint(ctl, "rss %llu\n", stats[i].val);
         if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_LAST_UPDATE)
             vshPrint(ctl, "last_update %llu\n", stats[i].val);
+        if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_DISK_CACHES)
+            vshPrint(ctl, "disk_caches %llu\n", stats[i].val);
     }
 
     ret = true;
diff --git a/tools/virsh.pod b/tools/virsh.pod
index dc100db9f3..50799cf588 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -924,6 +924,8 @@ B<Explanation of fields>:
   usable            - The amount of memory which can be reclaimed by balloon
 without causing host swapping (in KiB)
   last-update       - Timestamp of the last update of statistics (in seconds)
+  disk_caches       - The amount of memory that can be reclaimed without
+additional I/O, typically disk caches (in KiB)
 
 For QEMU/KVM with a memory balloon, setting the optional I<--period> to a
 value larger than 0 in seconds will allow the balloon driver to return
@@ -1030,6 +1032,9 @@ I<--balloon> returns:
                     balloon without causing host swapping (in KiB)
  "balloon.last-update" - timestamp of the last update of statistics
                          (in seconds)
+ "balloon.disk_caches " - the amount of memory that can be reclaimed
+                          without additional I/O, typically disk
+                          caches (in KiB)
 
 I<--vcpu> returns:
 
-- 
2.17.1