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SubjectRe: Blocked processes <=> Elevator starvation?
Jens Axboe wrote:

> On Sun, Oct 29 2000, Miles Lane wrote:
>
>>>> There were still some stalls but they only lasted a couple of
>>>> seconds. The patch did make a difference and for the better.
>>>
>>>
>>> Ok, still needs a bit of work. Thanks for the feedback.
>>
>> Have you resolved this problem completely, now?
>>
>> I am testing the USB Storage support with my ORB backup
>> drive. When I run:
>>
>> dd if=/dev/zero of=/dev/sda bs=1k count=2G
>>
>> The drive gets data quickly for about thirty seconds.
>> Then the throughput drops off to about ten percent
>> of its previous transfer rate. This dropoff appears to
>> be due to conflict over accessing filesystems. Specifically,
>> I have USB_STORAGE_DEBUG enabled, which shoots a ton of
>> debugging output into my kernel log. When the throughput
>> to the ORB drive falls off, all writing to the syslog
>> ceases. At least, that's what "tail -f" shows.
>>
>> I would be happy to test any patches you have for this
>> problem.
>
>
> Could you send vmstat 1 info from the start of the copy
> and until the i/o rate drops off?

I just reproduced the problem in test10-pre7. Here's the
output you requested:

vmstat 1
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 126308 5724 59480 0 0 23 9 162 306 6 2 92
0 0 0 0 126292 5724 59480 0 0 0 0 297 786 4 4 92
0 0 0 0 126292 5724 59480 0 0 0 0 210 593 2 1 97
1 2 2 0 59768 64308 59508 0 0 0 17425 950 37095 11 66 23
0 2 3 0 59460 64580 59508 0 0 0 645 317 1169 0 1 99
0 2 2 0 58672 65272 59508 0 0 0 657 293 1928 0 2 98
0 2 2 0 58272 65628 59508 0 0 0 647 283 1228 1 0 99
0 2 2 0 57868 65984 59508 0 0 0 647 284 1230 0 4 96
0 2 2 0 57464 66340 59508 0 0 0 648 284 1221 0 0 100
1 2 2 0 56600 67100 59512 0 0 0 662 295 2062 0 0 100
0 2 2 0 56192 67460 59512 0 0 0 522 285 1237 0 1 99
0 2 2 0 55888 67728 59512 0 0 0 644 282 1040 0 1 99
0 2 2 0 55484 68084 59512 0 0 0 646 285 1227 0 1 99
0 2 2 0 54648 68820 59512 0 0 0 661 299 2019 0 2 98
1 2 2 0 54240 69176 59512 0 0 0 648 406 1549 1 3 96
1 2 2 0 53824 69532 59512 0 0 0 649 637 2073 6 1 93
0 2 2 0 53424 69884 59516 0 0 0 649 466 1705 2 1 97
2 2 2 0 52172 70380 59516 0 0 0 656 1011 3612 14 4 82
3 2 2 0 51728 70716 59516 0 0 0 647 1994 2329 9 6 85
1 2 2 0 51312 71064 59516 0 0 0 636 1883 1517 12 9 79
2 2 2 0 50972 71420 59516 0 0 0 636 1092 1541 12 0 88
0 2 2 0 50100 72176 59520 0 0 0 671 611 2266 19 6 75
1 2 2 0 49692 72532 59520 0 0 0 638 305 682 1 1 98
1 2 2 0 49292 72888 59520 0 0 0 650 368 1574 0 1 99
0 2 2 0 48580 73516 59520 0 0 0 638 289 613 0 5 95
1 2 2 0 48180 73868 59520 0 0 0 636 278 542 1 0 99
0 2 2 0 47776 74224 59520 0 0 0 637 285 595 0 0 100
0 2 2 0 47372 74580 59520 0 0 0 636 274 513 0 8 92
0 2 2 0 46572 75288 59520 0 0 0 638 273 525 0 1 99
0 2 2 0 46168 75644 59520 0 0 0 637 281 588 0 2 98
0 2 2 0 45764 76000 59520 0 0 0 509 272 508 0 0 100
0 2 2 0 45300 76324 59520 0 0 0 636 276 548 1 0 99
0 2 2 0 44896 76680 59520 0 0 0 636 273 523 0 0 100
0 2 2 0 44088 77392 59520 0 0 0 650 281 1307 0 7 93
1 1 2 0 43736 77680 59548 0 0 0 1279 908 2637 1 8 91
0 2 3 0 43072 78040 59592 0 0 0 1660 1281 4119 5 6 89

>>> /var/log/kernel output stopped being emitted here <<<
>>> CRUNCH! <<<

0 2 3 0 42656 78384 59592 0 0 0 259 271 551 0 0 100
0 2 3 0 42656 78384 59592 0 0 0 5 271 499 0 0 100
0 2 3 0 42656 78384 59592 0 0 0 5 272 511 0 2 98
0 2 3 0 42656 78384 59592 0 0 0 4 268 502 0 0 100
0 2 3 0 42656 78384 59592 0 0 0 5 272 508 0 0 100
0 2 3 0 42656 78384 59592 0 0 0 5 274 523 0 0 100
0 2 3 0 42656 78384 59592 0 0 0 5 274 508 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
1 2 3 0 42656 78384 59592 0 0 0 5 273 515 0 0 100
0 2 3 0 42652 78384 59592 0 0 0 5 273 511 0 0 100
0 2 3 0 42652 78384 59592 0 0 0 5 273 513 0 0 100
0 2 3 0 42652 78384 59592 0 0 0 5 272 585 0 0 100
0 2 3 0 42652 78384 59592 0 0 0 5 291 946 0 0 100
1 2 3 0 42652 78384 59592 0 0 0 5 310 563 6 0 94
0 2 3 0 42652 78384 59592 0 0 0 5 272 520 0 0 100
1 2 3 0 42652 78384 59592 0 0 0 5 271 502 0 0 100
1 2 3 0 42648 78384 59592 0 0 0 5 300 608 0 0 100
1 2 3 0 42648 78384 59592 0 0 0 4 307 633 0 1 99
0 2 3 0 42648 78384 59592 0 0 0 5 276 526 0 0 100
1 2 3 0 42648 78384 59592 0 0 0 5 278 529 0 0 100
0 2 3 0 42648 78384 59592 0 0 0 5 274 512 0 4 96
1 2 3 0 42648 78384 59592 0 0 0 5 273 514 0 0 100
0 2 3 0 42648 78384 59592 0 0 0 5 272 511 0 0 100
1 2 3 0 42648 78384 59592 0 0 0 5 270 498 0 0 100
0 2 3 0 42648 78384 59592 0 0 0 5 271 512 0 0 100
1 2 3 0 42648 78384 59592 0 0 0 5 273 506 0 0 100
0 2 3 0 42648 78384 59592 0 0 0 5 386 926 3 0 97
1 2 3 0 42640 78384 59592 0 0 0 18 434 1072 2 2 96
0 2 3 0 42636 78384 59592 0 0 0 30 292 759 2 0 98

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