[libvirt] [PATCH] Add support L2 table cache for qcow2 disk

[dujiancheng]

  The patch add support L2 table cache for qcow2 disk.
  L2 table cache can improve IO read and write performance for qcow2 img.
  Example: random 4K read requests on a fully populated 100GB image (SSD backend and vm with directsync cacha mode),
           IOPS increased by 7 times.
  
---
 src/conf/domain_conf.c  | 25 +++++++++++++++++++++++++
 src/conf/domain_conf.h  |  4 ++++
 src/qemu/qemu_command.c |  7 +++++++
 src/qemu/qemu_domain.c  |  4 ++++
 4 files changed, 40 insertions(+)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index b8b5345..cb9fb05 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -9502,6 +9502,8 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
     char *vendor = NULL;
     char *product = NULL;
     char *domain_name = NULL;
+    char *disk_l2_cache_size = NULL;
+    char *disk_cache_clean_interval = NULL;
 
     if (!(def = virDomainDiskDefNew(xmlopt)))
         return NULL;
@@ -9701,6 +9703,27 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
             }
         } else if (virXMLNodeNameEqual(cur, "boot")) {
             /* boot is parsed as part of virDomainDeviceInfoParseXML */
+        } else if (virXMLNodeNameEqual(cur, "diskCache")) {
+            disk_l2_cache_size =
+                virXMLPropString(cur, "disk_l2_cache_size");
+            if (disk_l2_cache_size &&
+                virStrToLong_ui(disk_l2_cache_size, NULL, 0,
+                                &def->disk_cache.disk_l2_cache_size) < 0) {
+                virReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("invalid disk L2 cache size '%s'"),
+                               disk_l2_cache_size);
+                goto error;
+            }
+            disk_cache_clean_interval =
+                virXMLPropString(cur, "disk_cache_clean_interval");
+            if (disk_cache_clean_interval &&
+                virStrToLong_ui(disk_cache_clean_interval, NULL, 0,
+                                &def->disk_cache.disk_cache_clean_interval) < 0) {
+                virReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("invalid disk cache clean interval '%s'"),
+                               disk_cache_clean_interval);
+                goto error;
+            }
         }
     }
 
@@ -9903,6 +9926,8 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
     VIR_FREE(vendor);
     VIR_FREE(product);
     VIR_FREE(domain_name);
+    VIR_FREE(disk_l2_cache_size);
+    VIR_FREE(disk_cache_clean_interval);
 
     ctxt->node = save_ctxt;
     return def;
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 71437dc..6396475 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -647,6 +647,10 @@ struct _virDomainDiskDef {
         unsigned int physical_block_size;
     } blockio;
 
+    struct {
+        unsigned int disk_l2_cache_size;
+        unsigned int disk_cache_clean_interval;
+    } disk_cache;
     virDomainBlockIoTuneInfo blkdeviotune;
 
     char *driverName;
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 4fc3176..4bc9412 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1637,6 +1637,13 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
 
     if (qemuBuildDriveSourceStr(disk, qemuCaps, &opt) < 0)
         goto error;
+		
+    if (disk->disk_cache.disk_l2_cache_size > 0)
+        virBufferAsprintf(&opt, "l2-cache-size=%u,",
+                disk->disk_cache.disk_l2_cache_size);
+    if (disk->disk_cache.disk_cache_clean_interval > 0)
+        virBufferAsprintf(&opt, "cache-clean-interval=%u,",
+                disk->disk_cache.disk_cache_clean_interval);
 
     if (qemuDiskBusNeedsDeviceArg(disk->bus)) {
         char *drivealias = qemuAliasDiskDriveFromDisk(disk);
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index fee4481..4896bf7 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -8627,6 +8627,10 @@ qemuDomainDiskChangeSupported(virDomainDiskDefPtr disk,
     CHECK_EQ(ioeventfd, "ioeventfd", true);
     CHECK_EQ(event_idx, "event_idx", true);
     CHECK_EQ(copy_on_read, "copy_on_read", true);
+    CHECK_EQ(disk_cache.disk_l2_cache_size,
+             "diskCache disk_l2_cache_size", true);
+    CHECK_EQ(disk_cache.disk_cache_clean_interval,
+             "diskCache disk_cache_clean_interval", true);
     /* "snapshot" is a libvirt internal field and thus can be changed */
     /* startupPolicy is allowed to be updated. Therefore not checked here. */
     CHECK_EQ(transient, "transient", true);
-- 
1.8.3.1