[Bug 50741] Slow disk writes (ubuntu kernel)
Erik de Castro Lopo
erikd+ubuntu at mega-nerd.com
Wed Dec 20 02:37:35 UTC 2006
Public bug reported:
Runing the above kernel on a Dell Latitude X1 laptop. Disk writes
are very much slower with this kernel than with linux-image-2.6.15-23-686.
I have a test program which does a large amount of reading and
writing of files. On the -23 kernel this program runs in 16-18
seconds. On the -25 kernel the same binary takes from 1 -4
minutes. The machine is not doing much else at the time.
Here's the dstat output from the -23 kernel (write throughput about a
Meg a second)
----total-cpu-usage---- -disk/total -net/total- ---paging-- ---system--
usr sys idl wai hiq siq|_read write|_recv _send|__in_ _out_|_int_ _csw_
27 16 52 5 1 0| 111k 55k| 0 0 | 0 0 |1014 125
0 0 100 0 0 0| 0 0 |1364B 3230B| 0 0 |1021 61
43 29 29 0 0 0| 0 580k|1306B 3452B| 0 0 |1076 307
25 13 38 25 0 0| 0 1160k| 956B 5238B| 0 0 |1151 458
10 30 20 30 0 10| 0 1372k|1164B 6426B| 0 0 |1143 452
29 14 29 29 0 0| 0 1136k| 714B 4972B| 0 0 |1108 401
22 11 33 22 11 0|4096B 1224k| 918B 5894B| 0 0 |1155 480
22 22 33 22 0 0| 0 1356k|1377B 7408B| 0 0 |1164 490
27 9 27 27 9 0| 0 1424k| 950B 5588B| 0 0 |1177 665
29 14 29 29 0 0| 0 1216k|1020B 5288B| 0 0 |1155 508
25 25 38 13 0 0| 0 1100k| 816B 5206B| 0 0 |1154 439
22 22 33 22 0 0|4096B 1264k|1148B 5620B| 0 0 |1151 440
36 36 18 9 0 0| 0 1056k|1610B 8432B| 0 0 |1154 452
14 14 43 29 0 0| 0 1104k| 714B 4590B| 0 0 |1122 496
22 22 33 22 0 0| 0 1304k|1020B 6566B| 0 0 |1155 511
22 11 22 33 11 0| 0 1300k|1170B 3910B| 0 0 |1141 408
25 25 25 25 0 0| 0 980k|1402B 6814B| 0 0 |1133 432
11 33 33 22 0 0|4096B 1204k|1224B 6444B| 0 0 |1136 448
25 13 38 25 0 0| 0 1152k|1456B 5898B| 0 0 |1160 495
30 20 30 20 0 0| 0 1280k|1358B 8108B| 0 0 |1146 496
43 14 43 0 0 0| 0 348k|2303B 5166B| 0 0 |1098 206
And now the -25 output (about 1/10th the disk throughput):
----total-cpu-usage---- -disk/total -net/total- ---paging-- ---system--
usr sys idl wai hiq siq|_read write|_recv _send|__in_ _out_|_int_ _csw_
0 0 50 50 0 0| 0 136k| 166B 666B| 0 0 | 338 57
33 33 0 33 0 0| 0 60k| 448B 634B| 0 0 | 327 42
0 0 100 0 0 0| 0 124k| 166B 748B| 0 0 | 332 59
0 0 50 50 0 0| 0 40k| 166B 634B| 0 0 | 363 42
0 50 50 0 0 0| 0 140k| 246B 634B| 0 0 | 355 68
33 0 33 33 0 0| 0 84k| 236B 956B| 0 0 | 333 46
0 33 67 0 0 0| 0 96k| 344B 694B| 0 0 | 286 59
100 0 0 0 0 0| 0 80k| 166B 666B| 0 0 | 339 47
0 0 50 50 0 0| 0 68k| 294B 700B| 0 0 | 336 48
0 0 100 0 0 0| 0 132k| 230B 634B| 0 0 | 275 55
0 0 50 50 0 0| 0 100k| 294B 634B| 0 0 | 285 59
0 33 33 33 0 0| 0 72k| 470B 634B| 0 0 | 306 50
0 0 0 100 0 0| 0 88k| 358B 1242B| 0 0 | 349 55
50 0 50 0 0 0| 0 80k| 358B 650B| 0 0 | 324 47
33 0 33 33 0 0| 0 112k| 102B 666B| 0 0 | 356 63
0 50 50 0 0 0| 0 72k| 483B 1070B| 0 0 | 327 32
0 0 50 50 0 0| 0 120k| 306B 650B| 0 0 | 353 62
The hdparm settings are identical under both kernels:
/dev/hda:
multcount = 0 (off)
IO_support = 0 (default 16-bit)
unmaskirq = 0 (off)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 16383/255/63, sectors = 117210240, start = 0
I can't debug this any further, but happy to do testing if someone
has an idea.
Note: the original reporter indicated the bug was in package 'linux-image-2.6.15-25-686'; however, that package was not published in Baltix.
** Affects: linux-source-2.6.15 (Ubuntu)
Importance: Undecided
Status: Rejected
** Affects: Baltix
Importance: Undecided
Status: Rejected
--
Slow disk writes (ubuntu kernel)
https://launchpad.net/bugs/50741
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