Re: Time sliced CFQ io scheduler

Prakash K. Cheemplavam
2004-12-03T11:27:25Z

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Jens Axboe schrieb:
> On Fri, Dec 03 2004, Prakash K. Cheemplavam wrote:
>
>>>But at least this patch lets you set slice_sync and slice_async
>>>seperately, if you want to experiement.
>>
>>An idea, which values I should try?
>
>
> Just see if the default ones work (or how they work :-)
>
>>BTW, I just did my little test on the ide drive and it shows the same
>>problem, so it is not sata / libata related.
>
>
> Single read/writer case works fine here for me, about half the bandwidth
> for each. Please show some vmstats for this case, too. Right now I'm not
> terribly interested in problems with raid alone, as I can poke holes in
> that. If the single drive case is correct, then we can focus on raid.

I have not enough space to perform this test on the ide drive, so I did
it on the sata (single disk). The patch doesn't seem to be better. (But
on the other hand I haven't tested you first version on single disk.) At
least it still doesn't look good enough in my eyes.

procs -----------memory---------- ---swap-- -----io---- --system--
----cpu----
r b swpd free buff cache si so bi bo in cs us
sy id wa
1 3 2704 5368 1528 906540 0 4 2176 24068 1245 743 0
7 0 93
0 3 2704 5432 1532 906252 0 0 5072 28160 1277 782 1
8 0 91
0 5 2704 5688 1532 906080 0 0 9280 4524 1309 842 1
10 0 89
1 3 2704 5232 1544 906208 0 0 6404 76388 1285 716 1
14 0 85
0 3 2704 5496 1544 906524 0 0 8328 26624 1301 856 1
8 0 91
0 3 2704 5512 1528 906636 0 0 9484 22016 1302 883 1
8 0 91
0 3 2704 5816 1500 906296 0 0 5508 10288 1270 749 1
9 0 90
0 4 2704 5620 1488 906608 0 0 3076 19920 1267 818 0
13 0 87
1 4 2704 5684 1456 906432 0 0 3204 18432 1252 704 1
8 0 91
1 3 2704 5504 1408 906168 0 0 5252 28672 1279 777 1
14 0 85
0 4 2704 5120 1404 906296 0 0 8968 16384 1351 876 1
9 0 90
0 4 2704 5364 1404 905620 0 0 5252 26112 1339 835 1
14 0 85
0 4 2704 5600 1432 905036 0 0 1468 15876 1312 741 2
8 0 90
1 4 2704 5556 1424 904704 0 0 1664 26112 1243 714 1
10 0 89
0 4 2704 5492 1428 904100 0 0 1412 31232 1253 760 1
15 0 84
0 4 2704 5568 1432 903456 0 0 1668 29696 1253 703 1
14 0 85
1 4 2704 5620 1408 902980 0 0 1280 28672 1248 732 0
14 0 86
0 4 2704 5236 1404 902888 0 0 2180 28704 1252 705 1
11 0 88
0 4 2704 5632 1388 902180 0 0 1536 28160 1251 731 1
11 0 88
0 3 2704 5120 1356 905968 0 0 384 57896 1257 751 1
14 0 85

What I don't like about the time sliced cfq (first version as well) is
that I don't get good sustained rate anymore if I have only one writer
and nothing else. IIRC with plain cfq I at least got near to maximum
throughput (40-50mb/sec) now it oscillates much more. I have to recheck
with plain cfq though. It might be ext3 related...

0 2 2684 7016 9384 900664 0 0 0 59128 1217 576 1
7 0 92
1 1 2684 5160 9368 898660 0 0 0 12300 1239 4861 1
60 0 39
0 3 2684 5532 9364 896360 0 0 0 18684 1246 1723 1
48 0 51
0 3 2684 5596 9364 896616 0 0 0 24576 1246 686 1
9 0 90
0 3 2684 5596 9364 896612 0 0 0 38400 1261 718 0
13 0 87
0 3 2684 5532 9360 896564 0 0 0 37888 1257 708 1
13 0 86
0 3 2684 5532 8848 896884 0 0 0 36864 1260 825 1
12 0 87
1 3 2696 5596 7440 898120 0 0 0 31744 1247 703 1
11 0 88
0 3 2700 5660 5352 900080 0 0 0 37888 1258 768 1
13 0 86
0 2 2700 6816 5216 900436 0 0 0 68772 1266 783 1
25 0 74
0 2 2700 6884 5216 900436 0 0 0 19616 1247 679 2
1 0 97
1 2 2700 7096 5216 900436 0 0 0 14976 1249 786 1
3 0 96
0 2 2700 5352 4572 902432 0 0 4 66544 1263 2333 1
21 0 78

Prakash

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