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Re: [Xen-users] Big I/O performance difference between dom0 and domU

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Big I/O performance difference between dom0 and domU
From: Marcin Owsiany <marcin@xxxxxxxxxx>
Date: Wed, 18 Apr 2007 10:48:14 +0100
Cc: Liang Yang <multisyncfe991@xxxxxxxxxxx>
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On Tue, Apr 17, 2007 at 05:57:02PM +0100, Marcin Owsiany wrote:
> On Tue, Apr 17, 2007 at 09:34:10AM -0700, Liang Yang wrote:
> > What is the CPU utilization when you did this I/O performance measurement?
> 
> "% CPU" reported by bonnie when writing/reading/random seeking in is
> 6/3/0% in dom0 and 4/2/0% in domU. bonnie was the only thing running
> when performing the test.
> 
> > As far I can remember, Bonnie++ does not support using outstanding I/Os.
> > So your target RAID volume may not be saturated, i.e. you did not get the 
> > peak performance.
> 
> What other benchmarking tool would you suggest?

OK, I ran tiobench, which does a multi-threaded test. The conclusions are
basically the same, there is a HUGE performance drop when moving from dom0 to
domU.


Unit information
================
File size = megabytes
Blk Size  = bytes
Rate      = megabytes per second
CPU%      = percentage of CPU used during the test
Latency   = milliseconds
Lat%      = percent of requests that took longer than X seconds
CPU Eff   = Rate divided by CPU% - throughput per cpu load

======
=
= dom0
=
======

Sequential Reads
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1454  4096    1   59.41 4.243%     0.325      
136.06   0.00000  0.00000  1400
2.6.18-4-xen-686              1454  4096    2   55.44 7.004%     0.695      
640.86   0.00000  0.00000   792
2.6.18-4-xen-686              1454  4096    4   54.86 14.34%     1.403     
1794.06   0.00000  0.00000   382
2.6.18-4-xen-686              1454  4096    8   45.94 20.58%     3.231     
4126.18   0.00000  0.00000   223

Random Reads
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1454  4096    1    0.94 0.183%    20.700      
262.32   0.00000  0.00000   514
2.6.18-4-xen-686              1454  4096    2    1.61 0.049%    23.767       
99.26   0.00000  0.00000  3255
2.6.18-4-xen-686              1454  4096    4    2.29 0.328%    32.698      
203.58   0.00000  0.00000   698
2.6.18-4-xen-686              1454  4096    8    2.72 0.292%    49.862      
574.06   0.00000  0.00000   930

Sequential Writes
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1454  4096    1   10.48 7.397%     1.382    
18330.81   0.00243  0.00000   142
2.6.18-4-xen-686              1454  4096    2   10.08 14.59%     2.734    
41922.34   0.00994  0.00027    69
2.6.18-4-xen-686              1454  4096    4    9.74 28.07%     5.620   
108145.49   0.04493  0.00351    35
2.6.18-4-xen-686              1454  4096    8    9.56 53.08%    10.883   
105600.05   0.13138  0.00675    18

Random Writes
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1454  4096    1    1.23 0.819%     0.108        
0.55   0.00000  0.00000   150
2.6.18-4-xen-686              1454  4096    2    1.24 1.258%     0.125       
40.93   0.00000  0.00000    99
2.6.18-4-xen-686              1454  4096    4    1.22 1.970%     0.125       
74.78   0.00000  0.00000    62
2.6.18-4-xen-686              1454  4096    8    1.12 3.463%     0.107        
1.53   0.00000  0.00000    32


======
=
= domU
=
======

Sequential Reads
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1016  4096    1   47.22 2.435%     0.410      
107.34   0.00000  0.00000  1939
2.6.18-4-xen-686              1016  4096    2   50.51 6.466%     0.768      
149.37   0.00000  0.00000   781
2.6.18-4-xen-686              1016  4096    4   34.17 6.062%     2.270      
324.78   0.00000  0.00000   564
2.6.18-4-xen-686              1016  4096    8   30.68 10.90%     5.011      
843.47   0.00000  0.00000   281

Random Reads
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1016  4096    1    1.39 0.021%    14.048       
68.12   0.00000  0.00000  6510
2.6.18-4-xen-686              1016  4096    2    1.42 0.029%    27.293      
107.90   0.00000  0.00000  4883
2.6.18-4-xen-686              1016  4096    4    2.86 0.351%    26.259      
210.81   0.00000  0.00000   814
2.6.18-4-xen-686              1016  4096    8    4.08 0.334%    35.834      
401.12   0.00000  0.00000  1221

Sequential Writes
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1016  4096    1    6.98 4.370%     2.223     
8511.98   0.00000  0.00000   160
2.6.18-4-xen-686              1016  4096    2    6.00 7.388%     4.795    
18369.97   0.07612  0.00000    81
2.6.18-4-xen-686              1016  4096    4    5.88 13.93%     9.530    
39506.77   0.22645  0.00000    42
2.6.18-4-xen-686              1016  4096    8    5.27 22.37%    16.923    
79262.92   0.26606  0.01999    24

Random Writes
                              File  Blk   Num                   Avg      
Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    
Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- 
-----------  -------- -------- -----
2.6.18-4-xen-686              1016  4096    1    1.01 0.524%     0.101        
2.45   0.00000  0.00000   193
2.6.18-4-xen-686              1016  4096    2    1.03 0.975%     0.127       
85.29   0.00000  0.00000   106
2.6.18-4-xen-686              1016  4096    4    0.98 1.461%     0.102        
2.79   0.00000  0.00000    67
2.6.18-4-xen-686              1016  4096    8    0.93 2.610%     0.101        
2.49   0.00000  0.00000    36

-- 
Marcin Owsiany <marcin@xxxxxxxxxx>              http://marcin.owsiany.pl/
GnuPG: 1024D/60F41216  FE67 DA2D 0ACA FC5E 3F75  D6F6 3A0D 8AA0 60F4 1216
 
"Every program in development at MIT expands until it can read mail."
                                                              -- Unknown

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