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Message #89145
[Bug 1390354] Re: Ubuntu Server 14.04.1 as VirtualBox Guest disk performance drops with more than once CPU
I found the problem:
The stock Ubuntu Server 14.04.1 amd64 iso image currently downloadable
comes with a kernel which has the flag CONFIG_CONTEXT_TRACKING_FORCE=y .
Recompiling the kernel without this flag set or upgrading to a kernel
without the flag fixes the performance issues:
Multiple CPU, stock 14.04.1 kernel (3.13.0-32):
vagrant@ubuntu-14:~$ dd if=/dev/zero of=bigfile bs=1024 count=5000000
5000000+0 records in
5000000+0 records out
5120000000 bytes (5.1 GB) copied, 46.6511 s, 110 MB/s
Multiple CPUs, recompiled kernel (3.13.0-39 ; but I tested this specific
kernel with both flag enabled/disabled):
vagrant@ubuntu-14:~$ dd if=/dev/zero of=bigfile bs=1024 count=5000000
5000000+0 records in
5000000+0 records out
5120000000 bytes (5.1 GB) copied, 10.4548 s, 490 MB/s
It seems this specific flag has been brought up in another report (
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1349028 ) and is
already fixed/soon to be released.
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https://bugs.launchpad.net/bugs/1390354
Title:
Ubuntu Server 14.04.1 as VirtualBox Guest disk performance drops with
more than once CPU
Status in “linux” package in Ubuntu:
Confirmed
Bug description:
I'm running VirtualBox 4.3.18 on OSX 10.9.5 .
I install Ubuntu Server 14.04 64bit and performed this basic disk
write test:
dd if=/dev/zero of=bigfile bs=1024 count=5000000
Setup of host (MacBook Pro 2014):
- 16GB RAM
- 500GB SSD
The setup of the guest machine:
- 2GB RAM
- 60GB VDMK disk (only occupies 1-2 GB after minimal installation)
The result with 14.04 / 1 CPU: 13.6s / 376 MB /s
The result with 14.04 / 2 CPU: 41.5s / 123 MB /s
On 12.04 64bit with either 1 or 2 CPUs doesn't change the speed from
around 376 MB/s
I came up with this simple `dd` test after noticing that just many
things felt slow compared to my previous setup with 12.04. Running
puppet, database migration, etc. Everything noticeable degraded after
I ran a 14.04 with 2 CPUs.
The setup is made with the official 14.04 amd64 image and the standard
installation procedure (just saying yes to all dialogs), no
fancy/custom settings.
Things I tried:
- use different Motherboard chipset
- use IDE instead of SCSI (already during installation)
- use different IDE chipsets
I also created vmstat/iostat comparison (although I know about this
tool but can't make anything up with it's output):
Before writing the 5GB zeroes, I startet vmstat/iostat and quit it
afterwards; these are the logs. Maybe they help someone who
understands them?
vmstat with 1 CPU
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 0 1939068 16684 45944 0 0 2887 11 207 1421 5 9 85 0 0
1 0 0 1834700 16844 147360 0 0 160 0 136 143 5 21 73 1 0
0 1 0 1494508 16880 477948 0 0 32 196640 1742 215 17 80 0 3 0
1 0 0 1216688 16904 748316 0 0 12 336720 3065 357 13 83 0 4 0
1 1 0 916324 16912 1040380 0 0 8 300164 2490 275 15 85 0 0 0
1 1 0 623784 16924 1325020 0 0 12 290818 2590 304 14 86 0 0 0
1 0 0 331540 16932 1609576 0 0 8 277380 2602 261 15 84 0 1 0
1 0 92 84544 5816 1860588 0 92 8 266408 2373 275 14 85 0 1 0
3 0 416 69840 96 1880244 0 324 8 326136 2865 493 16 84 0 0 0
1 0 724 81064 88 1869532 0 308 12 366776 3180 556 16 84 0 0 0
1 0 1052 69352 92 1881392 0 328 12 336204 3074 541 17 82 0 1 0
1 1 1480 80160 96 1870952 0 428 16 345776 2909 506 16 84 0 0 0
1 0 1936 78492 104 1873396 0 456 12 347420 3146 547 16 81 0 3 0
1 0 2544 67684 96 1884676 0 608 8 320156 2890 481 17 83 0 0 0
3 1 3108 80780 96 1871980 0 564 12 350136 2974 507 16 83 0 1 0
2 0 3548 79064 84 1873748 0 440 12 355388 3107 570 16 84 0 0 0
1 0 3988 72260 96 1881724 0 440 16 319932 2990 505 17 83 0 0 0
0 0 4112 77012 248 1877096 0 124 2712 269248 2306 350 4 43 38 14 0
0 0 3980 75284 256 1878256 608 0 1748 76 63 110 0 2 97 1 0
### vmstat with 2 CPUs
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 4728 72916 772 1879116 1 8 166 17813 252 111 7 13 79 1 0
1 0 4728 1965416 852 37852 0 0 80 0 313 246 6 19 74 1 0
1 0 4728 1838368 852 161568 0 0 0 0 494 21 21 29 50 0 0
1 0 4728 1726976 856 269924 0 0 4 106516 1388 237 19 32 44 6 0
1 0 4728 1604976 860 388704 0 0 4 106500 1357 189 22 36 40 3 0
1 0 4728 1487140 880 503360 0 0 8 229588 2272 213 21 43 27 9 0
1 0 4728 1357332 880 629844 0 0 0 0 506 33 22 29 50 0 0
1 1 4728 1234228 884 749264 0 0 4 137664 1429 103 22 37 39 3 0
1 0 4728 1112300 888 867996 0 0 4 128772 1629 123 21 37 38 4 0
1 0 4728 987976 892 989032 0 0 4 106500 1329 83 22 35 41 3 0
1 0 4728 871432 912 1102492 0 0 12 229424 2270 246 21 43 27 9 0
1 0 4728 743556 912 1226964 0 0 0 0 486 18 22 29 50 0 0
2 0 4728 620096 916 1346932 0 0 4 108188 1338 98 21 36 40 3 0
1 0 4728 498700 920 1465012 0 0 4 158084 1737 145 22 39 35 4 0
1 0 4728 375956 924 1584600 0 0 4 106500 1335 92 22 36 40 3 0
1 0 4728 258288 940 1698692 0 0 8 225324 2223 210 21 43 27 9 0
1 0 4728 132520 940 1821260 0 0 0 0 501 20 22 29 50 0 0
1 0 4996 66768 112 1885580 0 268 220 106788 1511 219 19 34 41 5 0
1 2 5012 71568 116 1880736 0 16 8 134292 1479 314 22 37 38 3 0
1 0 5052 78080 116 1874516 0 40 4 132012 1719 275 21 40 36 4 0
1 0 5088 67908 120 1884508 0 36 4 225356 2301 361 22 44 26 8 0
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
1 0 5132 74848 112 1877920 0 44 0 44 589 263 22 29 49 0 0
1 0 5172 72924 112 1879676 0 40 4 106556 1385 249 21 37 40 3 0
1 1 5240 78988 116 1873796 0 68 4 137672 1476 277 22 37 38 3 0
1 0 5308 70256 116 1882532 0 68 4 128712 1699 257 22 39 36 4 0
1 0 5340 77468 136 1875524 0 32 16 225360 2289 366 21 44 27 8 0
2 0 5388 77840 128 1875324 0 48 0 48 580 242 22 30 49 0 0
2 0 5440 69500 120 1883484 0 52 4 106576 1387 248 22 37 39 3 0
2 0 5496 76928 124 1876008 0 56 4 117564 1407 275 22 36 40 3 0
1 0 5552 68904 124 1883932 0 56 4 148796 1754 281 21 40 35 4 0
1 0 5600 70356 136 1882664 0 48 8 225372 2320 381 22 44 26 8 0
1 0 5668 69292 132 1883832 0 68 0 68 572 241 22 30 49 0 0
1 0 5720 74508 132 1878824 0 52 0 106572 1393 258 21 37 39 3 0
1 0 5768 67348 120 1885924 0 48 4 106548 1494 272 22 37 39 3 0
1 1 5836 73112 120 1880196 0 68 4 145992 1566 299 21 38 37 4 0
1 0 5892 68260 132 1885004 0 56 8 239200 2562 400 22 46 24 9 0
1 0 5976 66812 128 1886448 0 84 0 84 588 246 21 30 49 0 0
1 0 6068 74444 132 1878868 0 92 4 106608 1407 316 22 36 39 3 0
1 0 6140 65820 124 1887572 0 72 4 106572 1389 253 22 37 40 3 0
1 1 6220 64992 124 1888248 0 80 4 137556 1506 288 22 37 38 3 0
1 0 6296 69388 140 1884176 0 76 12 247672 2625 421 21 46 23 9 0
1 0 6400 73392 124 1880312 0 104 0 104 599 237 22 30 49 0 0
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
1 0 6484 71628 124 1882636 0 84 656 106604 1419 276 22 37 39 3 0
0 1 6556 79784 120 1873452 0 72 8 221772 2087 355 17 37 39 7 0
0 0 6556 78296 120 1876500 0 0 3036 39232 574 195 0 5 93 2 0
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