> There should be no change in what bdflush actually does. I've been
> running 2.2.7-as-patched for 13 hours and it works fine; there was a
> six-hour compile job in that interval. I'm sure others can stress it
> harder though, I'd be interested in results.
I made a separate posting of this, but this one will have actual data in
it.
Your patch doesn't seem to scale up to heavy writes, like you might find
in a transaction-oriented database. Running without update, the bdflush
doesn't seem to be able to keep up with the I/O load (without making me
very nervous about recoverability and the age of buffers). Ideally, the
writes are done at a pace that's equal to a per-30-second sync, but spread
over the full 30 seconds. In other words, the ideal is what update used to
do. :-)
Here's the output of 'vmstat 2' during a collection of uniformly heavy
inserts, with update running as 'update -S -s 30' (so I can be sure of the
test parameters). Hopefully this will illustrate my point. Note how user
time drops: this is a result of the bursty I/O.
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 3628 8208 186092 10484 0 0 0 0 1134 42 95 5 0
2 0 0 3628 8192 186056 10484 0 0 1 0 1419 33 92 6 2
2 0 0 3628 8160 186088 10484 0 0 0 250 1648 58 86 8 6
2 0 0 3628 8324 186032 10484 0 0 1 0 896 12 91 3 6
2 0 0 3628 8148 186168 10484 0 0 1 250 1058 13 92 7 0
2 0 0 3628 8216 186120 10484 0 0 0 0 1191 19 95 5 0
2 0 0 3628 8156 186120 10484 0 0 1 0 1169 23 95 4 1
2 0 0 3728 8172 186204 10484 0 50 1 263 1112 51 93 5 2
2 0 1 3748 7928 186436 10484 0 10 0 3 1274 29 94 6 0
2 0 1 4112 8084 186648 10484 0 182 1 296 1397 121 90 8 2
2 0 0 4364 7768 187300 10484 0 126 0 32 1226 86 95 5 0
2 0 1 4396 5756 189152 10484 0 16 1 4 586 17 78 5 18
2 0 0 4452 8144 186876 10484 0 28 0 507 1055 26 92 8 0
2 0 0 4452 8188 186836 10484 0 0 1 250 1083 17 88 5 7
2 1 0 4452 8188 186780 10484 0 0 1 1520 1385 98 89 9 2
1 1 0 4452 8220 186748 10484 0 0 0 4599 1429 877 91 7 1
1 2 0 4452 8224 186744 10484 0 0 1 5390 1644 1043 76 11 13
2 0 0 4452 8112 186812 10484 0 0 0 128 706 29 88 5 6
2 0 0 4452 8172 186760 10484 0 0 1 0 896 12 96 3 0
2 0 0 4452 8284 186752 10484 0 0 0 500 1016 15 94 6 0
2 0 0 4452 8144 186880 10484 0 0 1 0 1087 18 95 4 1
2 0 0 4452 8248 186776 10484 0 0 1 0 1168 27 92 6 1
2 0 0 4452 8244 186776 10484 0 0 0 250 1333 18 96 4 0
1 0 0 4452 8236 186780 10484 0 0 0 0 1435 31 93 5 2
2 0 0 4452 8180 186836 10484 0 0 0 250 2013 115 84 8 7
2 0 0 4452 8276 186740 10484 0 0 0 0 1847 94 84 8 9
1 0 0 4452 8244 186772 10484 0 0 0 0 2068 102 86 9 6
2 0 0 4452 8184 186832 10484 0 0 1 250 1543 43 85 8 7
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