SIGs/PowerManagementBaseOS/Testcase Virtualized 32bit vs 64bit

The main aim of this test was comparison of syscall count, tick count, read/written bytes when performing the same task on virtual 32-bit and 64-bit machine.

System configuration

We used VirtualBox OSE and KVM to perform this test. All virtual machines run on the same physical machine (not simultaneously) in the same configuration.

• The host configuration:
  • Intel Core 2 Duo E8400 3GHz
  • 4 GB of memory
  • Fedora 11 (2.6.30.5-43.fc11.x86_64)
  • VirtualBox 3.0.4_OSE r50677
  • libvirt 0.6.2-17.fc11, qemu 2:0.10.6-4.fc11

• The guest configuration in VirtualBox:
  • 1 CPU (32bit or 64bit)
  • 1024 MB of memory
  • ACPI: enabled, PAE/NX: enabled, VT-x: enabled, Nested paging: enabled
  • Fedora Rawhide (2009-09-16), i686 or x86_64
  • VirtualBox Guest Additions

• The guest configuration in KVM
  • 1 CPU (i686 or x86_64)
  • 1024 MB or memory
  • Fedora Rawhide (2009-09-16), i686 or x86_64
  • virtio disk

Virtual disks conversion
The tests were run on VirtualBox machines at first. After that, the virtual disks were converted to QEMU format (qcow2) and used in KVM - to have the same installation.

Guest Additions for VirtualBox
Absence of Guest Additions has great influence on guest system performance especially when running 64-bit guest. If you are going to verify this test or create similar, don't forget to install Guest Additions before.

Test description

The results were measured using scomes (SystemTap script) which can be found in tuned-utils package. However we used the newest GIT version [1].

The test run 10 times in sequence. Clean caches, dentries and inodes were dropped before each run (echo 3 > /proc/sys/vm/drop_caches).

The measured task was building squid RPM package from src.rpm:

./scomes.stp -c "rpmbuild --rebuild squid-3.1.0.13-3.fc12.src.rpm" 0

Uprocessed results

VirtualBox 32-bit guest

	syscalls	kernel ticks	userspace ticks	read bytes	written bytes
1	176379	9169	5860	19815353	19496541
2	175957	9410	6057	19434866	19502130
3	175336	9341	5553	18696381	19489876
4	175072	9063	5522	18815017	19495984
5	175316	9186	5542	18788471	19495878
6	176232	9033	5353	19460705	19501778
7	174503	8979	5621	18517294	19489876
8	188483	21269	4921	31460765	20263640
9	189830	9248	5811	32850019	20232887
10	175268	19736	4881	18657208	19492557

VirtualBox 64-bit guest

	syscalls	kernel ticks	userspace ticks	read bytes	written bytes
1	175694	14905	8232	21770053	19564938
2	177300	14098	8037	19354317	19529482
3	179318	15268	7757	20555112	19549143
4	177070	9890	4724	18915315	19523128
5	177867	9826	4824	19321045	19529497
6	177306	10282	4792	18802447	19523195
7	178227	10220	4823	19181444	19531070
8	178271	9927	4855	19824862	19540823
9	178032	10149	4833	19304156	19529428
10	177906	10395	4798	19360721	19529566

KVM 32-bit guest

	syscalls	kernel ticks	userspace ticks	read bytes	written bytes
1	174540	8151	2571	19280444	19486683
2	174399	7673	2181	18968357	19495090
3	186836	7546	2224	30935608	20265990
4	174674	7487	2218	19028456	19494972
5	174393	7456	2193	18782550	19490383
6	174520	7380	2213	18857743	19487497
7	186927	7637	2216	30870324	20263823
8	174531	7415	2235	18720100	19490277
9	171019	7261	2073	15000148	19468860
10	187081	7662	2256	30930304	20265406

KVM 64-bit guest

	syscalls	kernel ticks	userspace ticks	read bytes	written bytes
1	173268	8092	1959	19782678	19532133
2	179307	8181	1979	19696304	19535759
3	179870	8234	1980	20019461	19549543
4	178176	8674	2130	19169793	19529757
5	176884	7736	2087	18466457	19518977
6	177183	6532	1975	18316321	19521145
7	177831	6413	1985	18794279	19521145
8	177022	6346	1864	18241975	19519216
9	177116	6447	1920	18445540	19523166
10	177891	6342	1905	18695531	19523532

Results

syscalls count

	VBox 32bit	VBox 64bit	KVM 32bit	KVM 64bit	VBox 32→64 increase	KVM 32→64 increase
average	178237.6	177699.1	177892	177454.8	-0.30%	-0.25%
median	175646.5	177886.5	174535.5	177507	1.28%	1.70%
min	174503	175694	171019	173268	0.68%	1.32%
max	189830	179318	187081	179870	-5.54%	-3.85%

ticks count

kernel

	VBox 32bit	VBox 64bit	KVM 32bit	KVM 64bit	VBox 32→64 increase	KVM 32→64 increase
average	11443.4	11496	7566.8	7299.7	0.46%	-3.53%
median	9217	10251	7516.5	7134	11.22%	-5.09%
min	8979	9826	7261	6342	9.43%	-12.66%
max	21269	15268	8151	8674	-28.21%	6.42%

userspace

	VBox 32bit	VBox 64bit	KVM 32bit	KVM 64bit	VBox 32→64 increase	KVM 32→64 increase
average	5512.1	5767.5	5512.1	1978.4	4.63%	-64.11%
median	5547.5	4828.5	5547.5	1977	-12.96%	-64.36%
min	4881	4724	4881	1864	-3.22%	-61.81%
max	6057	8232	6057	2130	35.91%	-64.83%

total

	VBox 32bit	VBox 64bit	KVM 32bit	KVM 64bit	VBox 32→64 increase	KVM 32→64 increase
average	16955.5	17263.5	13078.9	9278.1	1.82%	-29.06%
median	14961.5	15058.5	13040.5	9165	0.65%	-29.72%
min	14386	14614	12336	8210	1.58%	-33.45%
max	26190	23137	14011	10804	-11.66%	-22.89%

read/written bytes

read

	VBox 32bit	VBox 64bit	KVM 32bit	KVM 64bit	VBox 32→64 increase	KVM 32→64 increase
average	21649607.9	19638947.2	22137403.4	18962833.9	-9.29%	-14.34%
median	19124941.5	19337681	18998406.5	18744905	1.11%	-1.33%
min	18517294	18802447	15000148	18241975	1.54%	21,61%
max	32850019	21770053	30935608	20019461	-33.73%	-35.29%

written

	VBox 32bit	VBox 64bit	KVM 32bit	KVM 64bit	VBox 32→64 increase	KVM 32→64 increase
average	19646114.7	19535027	19720898.1	19527437.3	-0.57%	-0.98%
median	19496262.5	19529531.5	19492677.5	19523349	0.17%	0.16%
min	19489876	19523128	19468860	19518977	0.17%	0.26%
max	20263640	19564938	20265990	19549543	-3.45%	-3.54%

total

	VBox 32bit	VBox 64bit	KVM 32bit	KVM 64bit	VBox 32→64 increase	KVM 32→64 increase
average	41295722.6	39173974.2	41858301.5	38490271.2	-5.14%	-8.05%
median	38623998.5	38867170.5	38493437.5	38267243.5	0.63%	-0.59%
min	38007170	38325642	34469008	37761191	0.84%	9.55%
max	53082906	41334991	51201598	39569004	-22.13%	-22.72%

Conclusion

If we consider the average results to be predicative, it seems that there is almost no difference in syscall count between the architectures and virtualization tools.

As for the ticks: The 64-bit system under VirtualBox produced totally a bit more ticks than 32-bit system (mostly in userspace). In KVM the difference is much bigger, 64-bit system needs a bit more kernel ticks but far fewer user ticks, which makes totally approximately 30% ticks less than 32-bit system.

The difference in read/written bytes on both virtualization tools is not wide (as we expected). There is only i difference between 32-bit and 64-bit system. It seems that the second one is a bit better in read byte count.