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SubjectRe: IO performance problems in 2.4.19-pre5 when writing to DVD-RAM/ZIP/MO
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Roger Larsson <roger.larsson@skelleftea.mail.telia.com> writes:

> In an other recent thread "PROMBLEM: CD burning at 16x uses excessive CPU,
> although DMA is enabled" it was found out that writing to CD-R did not use
> DMA. This resulted in lots of wasted CPU cycles.

> > But even though 50% is quite high, CPU load is not the problem as such,
> > the problem is getting data to the writer fast enough. And it's not
> > happening. Even a single audio track that is completely cached so that
> > there is no HD access has problems. It's like somehow accessing the CD
> > writer hogs the system for such long periods that there is insufficient
> > time to fill the writing program's buffer.
>
> Might this be part of the problem in this case too? Moritz please time your
> commands

I have timed the new benchmarks. User time is 0, system time is 3% in
the worst case.

> and use vmstat too... (time spent in interrupt while running the
> idle process - does not always show up)

'vmstat 1' during benchmark 2 (reading from 130GB HDD, writing to
DVD-RAM), kernel 2.4.19-pre5, default bdflush parameters.

procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
1 5 2 10120 2932 7040 182276 0 6 344 501 135 217 4 2 94
1 0 2 10120 2184 7056 182976 0 0 8 0 116 115 2 2 96
0 1 2 10120 2244 7068 182932 0 0 0 3944 125 129 0 1 99
0 1 2 10120 2220 7072 182944 0 0 0 0 111 97 1 0 99
1 0 2 10120 2608 7080 182548 0 0 0 4032 136 123 1 0 99
1 0 3 10120 2676 7112 182448 0 0 4 40 168 155 1 1 98
1 1 2 10120 2180 7124 182928 0 0 4 0 112 104 1 2 97
0 1 2 10120 2192 7128 182924 0 0 0 4026 112 124 1 1 98
1 1 2 10120 2288 7132 182816 0 0 0 0 111 109 1 0 99
1 1 2 10120 2408 7136 182692 0 0 0 0 111 117 1 0 99
1 1 3 10120 2276 7160 182796 0 0 0 4044 116 142 1 1 98
1 1 2 10120 2216 7164 182840 0 0 4 12 108 92 1 0 99
1 1 2 10120 2320 7172 182744 0 0 0 0 115 132 1 1 98
1 0 2 10120 3168 7180 181888 0 0 0 4032 151 186 1 1 98
0 2 2 10120 2180 7188 182868 0 0 0 0 111 122 1 2 97
0 1 2 10120 2876 7188 182164 0 0 0 4032 111 113 1 4 95
0 2 3 10120 2772 7220 182244 0 0 0 40 113 133 1 3 96
0 1 2 10120 2192 7228 182824 0 0 0 0 116 123 1 2 97
0 1 2 10120 2300 7232 182704 0 0 0 0 111 116 1 0 99

[reading from HDD starts about here]

2 1 2 10120 2304 7256 181616 0 0 1172 4032 311 372 0 1 99
0 6 3 10120 2876 7272 180992 0 0 144 4048 113 124 0 0 100
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
0 2 3 10120 2284 7276 181672 0 0 1520 638 144 227 2 2 96
2 0 3 10120 2544 7284 181424 0 0 1020 0 161 177 1 1 98
3 0 3 10120 2820 7284 181216 0 0 1392 3876 186 209 1 1 98
0 3 3 10120 2504 7288 181536 0 0 980 0 127 133 0 1 99
2 0 3 10120 3124 7288 180972 0 0 1236 3890 220 258 2 0 98
0 2 3 10120 2596 7296 181564 0 0 0 0 113 137 1 1 98
0 2 3 10120 2204 7304 181992 0 0 516 0 122 127 1 2 97
0 2 3 10120 2416 7308 181816 0 0 240 3922 117 133 1 0 99
0 3 3 10120 2176 7312 182108 0 0 652 0 122 135 1 1 98
0 2 3 10120 2296 7316 181984 0 0 400 0 118 130 1 0 99
4 0 3 10120 2956 7316 181252 0 0 24 3930 173 200 1 1 98
0 4 3 10120 2184 7320 182048 0 0 1956 0 148 200 0 4 96
0 3 3 10120 2432 7324 181892 0 0 0 3968 111 133 0 1 99
2 0 3 10120 2544 7332 181804 0 0 1092 0 138 187 1 1 98
0 2 3 10120 2180 7336 182200 0 0 388 0 121 143 1 2 97
0 2 3 10120 2236 7340 182144 0 0 640 3968 121 148 1 1 98
0 3 3 10120 2560 7340 181760 0 0 616 0 124 138 1 3 96
0 2 3 10120 2484 7344 181932 0 0 76 0 113 128 1 2 97
5 0 3 10120 2640 7348 181780 0 0 832 3968 157 174 1 2 98
0 2 3 10120 2432 7352 182012 0 0 240 0 116 135 1 1 98
2 0 3 10120 2420 7360 182036 0 0 1348 3720 173 185 1 1 98


'vmstat 1' during benchmark 2 (reading from 130GB HDD, writing to
DVD-RAM), kernel 2.4.19-pre5,
'echo 2 500 0 0 500 3000 3 1 0 >/proc/sys/vm/bdflush'

procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
1 1 1 11020 110372 6956 78828 0 0 8 6946 116 88 1 10 89
0 1 2 11020 110344 6980 78832 0 0 0 44 120 96 1 0 99
0 1 1 11020 110344 6980 78832 0 0 0 3686 128 75 1 2 97
0 1 1 11020 110344 6980 78832 0 0 0 0 111 72 1 1 98
0 1 1 11020 110344 6980 78832 0 0 0 0 107 79 1 1 98
0 1 1 11020 110344 6980 78832 0 0 0 0 105 71 1 0 99
0 1 1 11020 110344 6980 78832 0 0 0 0 103 79 1 0 99
0 1 1 11020 102688 6996 86472 0 0 0 3942 111 93 1 5 94
0 1 1 11020 102688 6996 86472 0 0 0 0 114 79 0 1 99
0 1 1 11020 102684 6996 86476 0 0 0 3486 131 78 0 0 100
0 1 1 11020 102684 6996 86476 0 0 0 0 112 81 1 0 99
0 1 1 11020 94968 6996 94192 0 0 0 4372 111 84 1 5 94
1 1 2 11020 75780 7020 112368 0 0 18176 40 403 638 1 15 84
1 1 1 11020 46204 7028 141936 0 0 29576 0 582 971 1 23 76
3 1 1 11020 17368 7064 170736 0 0 28836 0 574 928 2 25 73
1 1 2 11020 4336 7092 186864 0 0 28188 3810 570 1024 1 22 77
1 1 1 11020 4436 7096 186760 0 0 27548 0 553 1155 1 19 80
1 1 1 11020 4388 5860 189088 0 1088 28704 1088 587 1190 2 25 73
1 1 1 11020 4460 5892 188984 0 0 29856 40 590 1243 1 24 75
1 1 1 11020 3204 5936 190232 0 0 27032 3540 550 1126 1 26 73
1 1 2 11020 3572 5964 189848 0 0 28828 0 570 1232 1 19 80
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
2 1 1 11020 4440 5992 188952 0 0 27292 3636 563 1147 1 21 78
1 1 1 11052 4416 6028 190044 0 824 28584 824 588 1225 1 26 73
0 2 3 11052 2256 6060 192168 0 0 16068 12 375 685 1 11 88

[reading and writing takes place concurrently at normal speed, but
there are still some "dropouts"]

0 2 1 11052 2276 6060 192120 0 0 0 2686 110 97 1 2 97
5 0 1 11052 2592 6060 191720 0 0 0 0 417 208 0 1 99
1 1 1 11052 3248 6132 191192 0 0 26472 5260 542 1212 1 31 68
2 1 1 11052 4384 6160 190040 0 0 28572 0 572 1173 1 20 79
2 1 1 11052 3716 6188 190680 0 0 27548 3844 570 1171 1 23 76
1 1 1 11052 4460 6216 189912 0 0 28316 0 570 1197 1 17 82
1 1 1 11704 2244 6244 192928 0 280 29096 280 595 1011 1 28 71
1 1 2 11704 3208 6300 191932 0 0 27678 4478 564 1123 1 25 74
1 1 2 11704 3332 6304 191828 0 0 29468 8 585 1229 1 27 72
1 1 2 11704 3416 6332 191700 0 0 30236 0 589 1253 1 19 80
0 2 2 11704 4400 6364 190676 0 444 29080 444 589 1241 1 24 75
1 1 1 12956 4372 6384 190968 0 508 28708 3450 588 1204 1 25 74
1 1 1 12956 4348 6412 190972 0 0 27296 0 569 1133 1 20 79
1 1 1 12956 3312 6416 192012 0 0 19092 0 417 801 1 15 84
1 1 1 12956 3308 6444 192012 0 0 28572 0 571 1181 1 25 74
1 1 1 12956 3284 6472 192012 0 0 28444 0 568 1178 1 26 73
1 1 1 12956 3284 6576 192312 0 68 26524 8276 548 1228 1 30 69
1 1 1 13944 4396 6600 191672 0 1060 29468 1060 599 1243 1 23 76


Moritz


--
Dipl.-Phys. Moritz Franosch
http://Franosch.org
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