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Re: [Xen-devel] Performance issues on dom0
Hi,
There are a few tests (like Pipe Throughput , Pipe-based Context
Switching) which give very bad results under xen enabled kernel. I
benchmarked similar results and I am not sure why.
Also I am not sure how these may effect real server performance. I
believe that running an apache (or any other service) and sending
requests to it on xen enabled vs vanilla kernel makes more sense to
measure the performance differences.
Below is the performance comparison between two.
|
Non-xen kernel |
xen kernel |
| Execl Throughput |
1 |
0.28 |
| File Copy 1024 bufsize 2000 maxblocks |
1 |
0.76 |
| File Copy 256 bufsize 500 maxblocks |
1 |
0.78 |
| File Copy 4096 bufsize 8000 maxblocks |
1 |
0.71 |
| Pipe Throughput |
1 |
0.25 |
| Pipe-based Context Switching |
1 |
0.31 |
| Process Creation |
1 |
0.25 |
| Shell Scripts (1 concurrent) |
1 |
0.36 |
| Shell Scripts (16 concurrent) |
1 |
0.39 |
| Shell Scripts (8 concurrent) |
1 |
0.39 |
| System Call Overhead |
1 |
0.53 |
regards,
OZ
2009/8/18 Fréric VANNIÈE <frederic@xxxxxxxxxxx>
Hello,
I'm benching a brand new Nehalem server and I've noticed performance problems when running xen0 without any VMs.
Xen : 3.4.1
OS: Debian 5.0 amd64
HW: Supermicro Dual-Xeon Nehalem L5520 2,27 GHz, 24GB memory, 16 CPUS (8 cores * 2 HT)
native kernel : 2.6.30.4
dom0 kernel 1 : 2.6.18-xen0
dom0 kernel 2 : 2.6.30.2-xen0 (SuSe patchs + config from http://x17.eu/xen)
Benchs: tar xjf linux2.6.30.4.tar.bz2
build 2.6.30.4 with the default config and "make -j16"
filebench (mail)
unixbench -c 16 system
The performances of 2.6.18-xen0 and 2.6.30.2-xen0 are very close (2.6.30 is a little faster) and the filesystem benchmark gives the same values for all kernels.
The dom0 has all the memory, all the vCPUS, no VMs is running, and each vCPU is pinned on a rCPU.
Linux elrond 2.6.30.2-xen0 #4 SMP Fri Aug 14 14:31:11 CEST 2009 x86_64 GNU/Linux
Name ID Mem VCPUs State Time(s)
Domain-0 0 24147 16 r----- 23128.5
1. tar xjf
- native : 13 seconds
- dom0 : 21 seconds
2. make -j16 linux :
- native : 56 seconds
- dom0 : 67 seconds
3. filebench :
- native : 4268 iops
- dom0 : 4219 iops
4. unixbench :
- native : 5262
- dom0 : 2200 !!!! --> very bad (1810 with 2.6.18-xen0)
Any idea on the cause ?
Regards,
=========== Unixbench : native ==============
Benchmark Run: mar aoû2009 13:24:36 - 13:51:10
16 CPUs in system; running 16 parallel copies of tests
Execl Throughput 40751.3 lps (30.0 s, 2 samples)
File Copy 1024 bufsize 2000 maxblocks 395854.5 KBps (30.0 s, 2 samples)
File Copy 256 bufsize 500 maxblocks 103076.1 KBps (30.0 s, 2 samples)
File Copy 4096 bufsize 8000 maxblocks 1363078.3 KBps (30.0 s, 2 samples)
Pipe Throughput 15770868.9 lps (10.0 s, 7 samples)
Pipe-based Context Switching 3671269.3 lps (10.0 s, 7 samples)
Process Creation 110360.2 lps (30.0 s, 2 samples)
Shell Scripts (1 concurrent) 65731.1 lpm (60.0 s, 2 samples)
Shell Scripts (16 concurrent) 4916.5 lpm (60.1 s, 2 samples)
Shell Scripts (8 concurrent) 9776.3 lpm (60.0 s, 2 samples)
System Call Overhead 6840143.9 lps (10.0 s, 7 samples)
System Benchmarks Partial Index BASELINE RESULT INDEX
Execl Throughput 43.0 40751.3 9477.1
File Copy 1024 bufsize 2000 maxblocks 3960.0 395854.5 999.6
File Copy 256 bufsize 500 maxblocks 1655.0 103076.1 622.8
File Copy 4096 bufsize 8000 maxblocks 5800.0 1363078.3 2350.1
Pipe Throughput 12440.0 15770868.9 12677.5
Pipe-based Context Switching 4000.0 3671269.3 9178.2
Process Creation 126.0 110360.2 8758.7
Shell Scripts (1 concurrent) 42.4 65731.1 15502.6
Shell Scripts (16 concurrent) --- 4916.5 ---
Shell Scripts (8 concurrent) 6.0 9776.3 16293.8
System Call Overhead 15000.0 6840143.9 4560.1
========
System Benchmarks Index Score (Partial Only) 5262.1
=========== Unixbench : dom0 2.6.30.2 ==============
Benchmark Run: mar aoû2009 15:07:45 - 15:34:31
16 CPUs in system; running 16 parallel copies of tests
Execl Throughput 11593.1 lps (29.9 s, 2 samples)
File Copy 1024 bufsize 2000 maxblocks 299238.3 KBps (30.0 s, 2 samples)
File Copy 256 bufsize 500 maxblocks 79926.1 KBps (30.0 s, 2 samples)
File Copy 4096 bufsize 8000 maxblocks 974072.8 KBps (30.0 s, 2 samples)
Pipe Throughput 3922840.5 lps (10.1 s, 7 samples)
Pipe-based Context Switching 1125963.3 lps (10.0 s, 7 samples)
Process Creation 27045.1 lps (30.0 s, 2 samples)
Shell Scripts (1 concurrent) 23418.9 lpm (60.0 s, 2 samples)
Shell Scripts (16 concurrent) 1939.5 lpm (60.2 s, 2 samples)
Shell Scripts (8 concurrent) 3826.3 lpm (60.1 s, 2 samples)
System Call Overhead 3592086.9 lps (10.1 s, 7 samples)
System Benchmarks Partial Index BASELINE RESULT INDEX
Execl Throughput 43.0 11593.1 2696.1
File Copy 1024 bufsize 2000 maxblocks 3960.0 299238.3 755.7
File Copy 256 bufsize 500 maxblocks 1655.0 79926.1 482.9
File Copy 4096 bufsize 8000 maxblocks 5800.0 974072.8 1679.4
Pipe Throughput 12440.0 3922840.5 3153.4
Pipe-based Context Switching 4000.0 1125963.3 2814.9
Process Creation 126.0 27045.1 2146.4
Shell Scripts (1 concurrent) 42.4 23418.9 5523.3
Shell Scripts (16 concurrent) --- 1939.5 ---
Shell Scripts (8 concurrent) 6.0 3826.3 6377.2
System Call Overhead 15000.0 3592086.9 2394.7
========
System Benchmarks Index Score (Partial Only) 2200.0
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