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Subject[DATAPOINT] -ac16+ and increased readahead (ksoftirqd related?)
Date
Hi,

After receiving Robert Cohens mail concerning
"[BENCH] Problems with IO throughput and fairness with 2.4.10 and 2.4.9-ac15"
I replied about the possibility to increase READAHEAD again.

But since I was running the -ac16 (with swapoff patch) I decided to try it
myself...

First my attempts were not that sucessful. Changing /proc/sys/vm/max-readahead
did not have any visible effect... (why not???)

Then I found /proc/ide/hda/settings
and changed "file_readahead:511" but got wery strange results...

The start is very good but suddenly the HD starts to sound strange. A check
with vmstat shows that there is a huge amount of context switches...

Going back to zero (global) readahead did not help.
So I rebooted the computer for more careful testing.

vmstat-3 is output from vmstat 3
file_readahead.settings is how I change the file_readahead

The test I perform, for each value of file_readahead, is a diff between
two huge, but identical, files.

/RogerL

--
Roger Larsson
Skellefteå
Sweden


procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
1 0 0 0 211740 2284 25312 0 0 409 36 143 145 9 9 82
0 0 0 0 211696 2284 25316 0 0 0 0 103 34 0 0 100
0 0 0 0 211012 2288 25316 0 0 1 15 111 67 1 0 99
0 0 0 0 211012 2288 25316 0 0 0 7 109 48 0 0 100
0 0 0 0 211000 2296 25320 0 0 4 0 107 48 0 0 100
0 0 0 0 210996 2296 25320 0 0 0 0 106 43 0 0 100
0 0 0 0 210996 2296 25320 0 0 0 0 104 37 0 0 100
0 0 0 0 210996 2296 25320 0 0 0 0 115 60 0 0 100
0 0 0 0 210980 2300 25328 0 0 4 19 115 57 0 0 100
0 1 0 0 210616 2308 25444 0 0 41 0 109 52 0 0 100
0 1 0 0 181632 2348 53680 0 0 9425 0 319 193 2 3 95
0 1 0 0 148800 2380 85680 0 0 10677 0 268 153 2 6 92
0 1 0 0 118084 2412 115616 0 0 9988 3 258 136 2 3 96
1 0 0 0 85768 2436 147120 0 0 10511 39 273 170 2 5 94
1 0 0 0 53720 2468 178352 0 0 10421 0 262 145 3 3 94
1 0 0 0 23252 2500 208048 0 0 9909 0 263 145 2 3 95
0 1 0 0 3056 2532 228868 0 0 10421 0 283 144 3 4 93
1 0 0 0 3056 2564 228836 0 0 10677 0 267 155 2 4 94
1 0 0 0 3056 2588 228812 0 0 10760 1 269 150 3 5 92
0 1 0 0 3056 2620 228780 0 0 10848 0 269 150 3 6 91
0 1 0 0 3056 2652 228748 0 0 9824 17 277 145 1 2 97
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
1 1 0 0 3056 2684 228716 0 0 11019 0 274 157 1 6 93
0 1 0 0 3056 2716 228560 0 0 10421 0 265 152 3 7 90
1 0 0 0 3056 2748 228528 0 0 10677 3 268 154 2 3 95
0 1 0 0 3056 2780 228496 0 0 10763 0 268 158 3 6 92
1 0 0 0 3056 2812 228464 0 0 11189 0 276 159 6 6 88
0 1 0 0 3056 2844 228432 0 0 11019 0 272 157 2 4 94
0 1 0 0 3056 2876 228400 0 0 11275 0 276 155 3 3 95
0 1 0 0 3056 2928 228324 0 0 10208 0 266 179 5 4 91
0 1 0 0 3056 2952 228268 0 0 10077 0 257 141 2 5 93
0 0 0 0 3280 2976 228248 0 0 7517 0 224 133 3 2 95
0 0 0 0 3280 2976 228248 0 0 0 0 104 37 0 0 100
0 0 0 0 3280 2976 228248 0 0 0 1 104 33 0 0 100
0 0 0 0 3280 2976 228248 0 0 0 0 105 39 0 0 100
- - -
0 0 0 0 3256 2976 228280 0 0 0 0 102 28 0 0 100
0 0 0 0 3256 2976 228280 0 0 0 4 103 32 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
2 0 0 0 3056 2976 228252 0 0 1035 0 127 55 0 1 99
0 1 0 0 3056 2976 230812 0 0 32960 0 373 158 7 8 85
0 1 1 0 3056 2976 228184 0 0 29047 1 366 63 16 10 75
0 1 0 0 3056 2976 228380 0 0 29581 0 345 40 4 8 88
0 2 0 0 3056 2976 228420 0 0 27116 0 344 40 0 3 97
1 0 0 24 3056 2976 228424 0 0 15897 0 1415 2300 3 9 88
0 1 0 28 3056 2976 228448 0 0 1211 0 403 631 0 2 98
1 0 0 28 3056 2976 228448 0 0 957 1 341 504 0 1 99
0 1 0 28 3056 2976 228448 0 0 9155 0 2389 4600 4 11 86
0 1 0 28 3056 2976 228448 0 0 1208 1 403 631 0 1 99
1 0 1 36 3056 2976 228448 0 0 9765 0 490 805 1 3 96
0 1 0 84 3056 2976 228504 0 0 29689 20 339 46 0 3 97
0 0 0 84 3272 2976 228516 0 0 4432 12 226 34 0 1 98
0 0 0 84 3272 2976 228516 0 0 0 0 100 24 0 0 100
0 0 0 84 3272 2976 228516 0 0 0 0 101 27 0 0 100
0 0 0 84 3268 2976 228520 0 0 1 0 103 35 0 0 100
0 0 0 84 3268 2976 228520 0 0 0 0 103 32 0 0 100
0 0 0 84 3268 2976 228520 0 0 0 0 105 36 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 0 0 84 3268 2976 228520 0 0 0 0 103 32 0 0 100
0 0 0 84 3264 2976 228524 0 0 1 0 108 44 0 0 100
0 0 0 84 3264 2976 228524 0 0 0 0 106 39 0 0 100
0 0 0 84 3264 2976 228524 0 0 0 0 100 27 0 0 100
0 0 0 84 3168 2976 228620 0 0 92 0 112 56 0 0 100
0 0 0 84 3168 2976 228620 0 0 0 0 103 28 0 0 100
0 1 0 84 3056 2976 228504 0 0 153 0 113 53 0 0 100
1 0 1 96 3056 2976 228516 0 0 32661 3 371 143 3 8 89
0 1 0 400 3056 2976 228620 0 0 27697 1 355 44 1 5 94
0 1 0 876 3056 2976 228656 0 0 29541 1 346 42 4 9 87
0 1 0 1040 3056 2976 228636 0 0 27267 0 344 41 0 6 94
0 1 0 1184 3056 2976 228652 0 0 9421 0 360 234 0 2 98
0 1 0 1184 3056 2976 228652 0 0 2032 0 609 1042 0 3 97
0 1 0 1256 3056 2976 228656 0 0 4756 0 1289 2404 2 5 93
0 1 0 1256 3056 2976 228656 0 0 1431 9 460 742 0 2 98
0 1 0 1256 3056 2976 228656 0 0 1105 0 377 576 0 0 99
0 1 0 1256 3056 2976 228656 0 0 893 0 324 471 0 1 99
1 1 0 1256 3056 2976 228656 0 0 1016 0 354 533 0 2 97
0 1 0 1256 3056 2976 228656 0 0 955 15 344 508 0 2 98
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
1 0 0 1256 3272 2976 228668 0 0 211 1 157 140 0 0 100
0 0 0 1256 3268 2976 228672 0 0 1 0 101 28 0 0 100
0 0 0 1256 3268 2976 228672 0 0 0 1 101 27 0 0 100
- - -
0 0 0 1256 3268 2976 228672 0 0 0 0 104 36 0 0 100
0 0 0 1256 3268 2976 228672 0 0 0 1 108 44 0 0 100
0 0 0 1256 3168 2976 228772 0 0 87 0 111 50 0 1 99
0 0 0 1256 3168 2976 228772 0 0 0 1 105 37 0 0 100
0 0 0 1256 3168 2976 228772 0 0 0 0 100 27 0 0 100
0 0 0 1256 3164 2976 228776 0 0 0 1 101 23 0 0 100
0 1 0 1336 3056 2976 228668 0 0 26984 1 331 161 3 5 92
0 1 0 1404 3056 2976 228672 0 0 27827 0 357 42 3 12 85
0 1 0 1464 3056 2976 228688 0 0 29128 0 346 40 0 5 95
0 1 0 1476 3056 1096 230572 0 0 27323 0 343 42 0 5 95
1 0 0 1476 3056 1096 230572 0 0 6079 0 385 342 0 1 98
0 1 0 1476 3056 1096 230572 0 0 1632 0 508 844 0 2 98
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
1 1 0 1476 3056 1096 230572 0 0 1916 0 589 1003 0 2 98
0 0 0 1476 3272 1096 230584 0 0 1109 11 387 595 0 1 98
0 0 0 1476 3268 1096 230584 0 0 0 3 101 26 0 0 100
0 0 0 1476 3268 1096 230584 0 0 0 0 101 27 0 0 100
0 0 0 1476 3268 1096 230584 0 0 0 15 109 38 0 0 100
0 0 0 1476 3268 1096 230584 0 0 0 0 121 77 0 0 100
1 0 0 1476 3268 1096 230584 0 0 0 0 108 43 0 0 100
0 0 0 1476 3268 1096 230584 0 0 0 0 106 39 0 0 100
0 0 0 1476 3268 1096 230584 0 0 0 0 102 29 0 0 100
0 0 0 1476 3168 1096 230684 0 0 87 0 114 60 0 0 100
0 1 0 1476 3056 1096 230568 0 0 335 0 185 194 0 1 99
1 0 0 1476 3056 1096 230568 0 0 1199 0 401 627 1 1 98
0 1 0 1476 3056 1096 230568 0 0 1263 0 416 658 0 2 97
0 1 0 1476 3056 1096 230568 0 0 1183 0 396 618 0 2 97
0 1 0 1476 3056 1096 230568 0 0 747 1 288 400 1 0 99
1 0 0 1476 3056 1096 230568 0 0 1792 0 549 920 0 3 97
0 1 0 1476 3056 1096 230568 0 0 1405 1 452 729 0 1 98
0 1 0 1476 3056 1096 230568 0 0 841 0 311 447 0 0 100
0 1 0 1476 3056 1096 230568 0 0 1261 0 416 656 0 1 99
1 0 0 1476 3056 1096 230568 0 0 1975 11 597 1011 0 1 98
file_readahead 0 0 2097151 rw
file_readahead 31 0 2097151 rw
file_readahead 511 0 2097151 rw
file_readahead 1023 0 2097151 rw
file_readahead 0 0 2097151 rw
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