diff --git a/Makefile.work b/Makefile.work
index ba392f5e1dad..ae15b1ec906d 100644
--- a/Makefile.work
+++ b/Makefile.work
@@ -27,6 +27,9 @@
 #  *                  make NOSTRETCH=1 KEEP_SLAVE_ON=yes <any jessie target>
 #  * SOURCE_FOLDER: host path to be mount as /var/$(USER)/src, only effective when KEEP_SLAVE_ON=yes
 #  * SONIC_BUILD_JOBS: Specifying number of concurrent build job(s) to run
+#  * VS_PREPARE_MEM: Prepare memory in VS build (drop cache and compact).
+#  *                 Default: yes
+#  *                 Values:  yes, no
 #  * KERNEL_PROCURE_METHOD: Specifying method of obtaining kernel Debian package: download or build
 #
 ###############################################################################
@@ -115,6 +118,7 @@ SONIC_BUILD_INSTRUCTION :=  make \
                            PASSWORD=$(PASSWORD) \
                            USERNAME=$(USERNAME) \
                            SONIC_BUILD_JOBS=$(SONIC_BUILD_JOBS) \
+                           VS_PREPARE_MEM=$(VS_PREPARE_MEM) \
                            KERNEL_PROCURE_METHOD=$(KERNEL_PROCURE_METHOD) \
                            HTTP_PROXY=$(http_proxy) \
                            HTTPS_PROXY=$(https_proxy) \
diff --git a/build_kvm_image.sh b/build_kvm_image.sh
index b08db96f573c..bc0f54e12d5c 100755
--- a/build_kvm_image.sh
+++ b/build_kvm_image.sh
@@ -1,4 +1,4 @@
-#!/bin/sh -ex
+#!/bin/bash -ex
 
 #  Copyright (C) 2014 Curt Brune <curt@cumulusnetworks.com>
 #
@@ -47,6 +47,15 @@ prepare_installer_disk()
 create_disk
 prepare_installer_disk
 
+echo "Prepare memory for KVM build: $vs_build_prepare_mem"
+free -m
+if [[ "$vs_build_prepare_mem" == "yes" ]]; then
+    # Force o.s. to drop cache and compact memory so that KVM can get 2G memory
+    sudo bash -c 'echo 1 > /proc/sys/vm/drop_caches'
+    sudo bash -c 'echo 1 > /proc/sys/vm/compact_memory'
+    free -m
+fi
+
 /usr/bin/kvm -m $MEM \
     -name "onie" \
     -boot "order=cd,once=d" -cdrom "$ONIE_RECOVERY_ISO" \
diff --git a/rules/config b/rules/config
index 5fa19928e0a9..f72573b1388a 100644
--- a/rules/config
+++ b/rules/config
@@ -84,3 +84,6 @@ DEFAULT_KERNEL_PROCURE_METHOD = build
 # group during installation.
 FRR_USER_UID = 300
 FRR_USER_GID = 300
+
+# Default VS build memory preparation
+DEFAULT_VS_PREPARE_MEM = yes
diff --git a/slave.mk b/slave.mk
index d2ac344adc84..294cf85ac887 100644
--- a/slave.mk
+++ b/slave.mk
@@ -120,6 +120,10 @@ ifeq ($(SONIC_BUILD_JOBS),)
 override SONIC_BUILD_JOBS := $(SONIC_CONFIG_BUILD_JOBS)
 endif
 
+ifeq ($(VS_PREPARE_MEM),)
+override VS_PREPARE_MEM := $(DEFAULT_VS_PREPARE_MEM)
+endif
+
 ifeq ($(KERNEL_PROCURE_METHOD),)
 override KERNEL_PROCURE_METHOD := $(DEFAULT_KERNEL_PROCURE_METHOD)
 endif
@@ -167,6 +171,7 @@ $(info "SONIC_PROFILING_ON"              : "$(SONIC_PROFILING_ON)")
 $(info "KERNEL_PROCURE_METHOD"           : "$(KERNEL_PROCURE_METHOD)")
 $(info "BUILD_TIMESTAMP"                 : "$(BUILD_TIMESTAMP)")
 $(info "BLDENV"                          : "$(BLDENV)")
+$(info "VS_PREPARE_MEM"                  : "$(VS_PREPARE_MEM)")
 $(info )
 
 ###############################################################################
@@ -175,6 +180,7 @@ $(info )
 ###############################################################################
 
 export kernel_procure_method=$(KERNEL_PROCURE_METHOD)
+export vs_build_prepare_mem=$(VS_PREPARE_MEM)
 
 ###############################################################################
 ## Local targets