RESOLVED: Re: Wierd context-switching issue on Xeon

Tom, Josh,

I think we have the problem resolved after I found the following note
from Tom:

> A large number of semops may mean that you have excessive contention
on some lockable
> resource, but I don't have enough info to guess what resource.

This was the key to look at: we were missing all indices on table which
is used heavily and does lots of locking. After recreating the missing
indices the production system performed normal. No, more excessive
semop() calls, load way below 1.0, CS over 20.000 very rare, more in
thousands realm and less.

This is quite a relief but I am sorry that the problem was so stupid and
you wasted some time although Tom said he had also seem excessive
semop() calls on another Dual XEON system.

Hyperthreading was turned off so far but will be turned on again the
next days. I don't expect any problems then.

I'm not sure if this semop() problem is still an issue but the database
behaves a bit out of bounds in this situation, i.e. consuming system
resources with semop() calls 95% while tables are locked very often and
longer.

Thanks for your help,

Dirk

At last here is the current vmstat 1 excerpt where the problem has been
resolved:

procs -----------memory---------- ---swap-- -----io---- --system--
----cpu----
r b swpd free buff cache si so bi bo in cs us sy
id wa
1 0 2308 232508 201924 6976532 0 0 136 464 628 812 5
1 94 0
0 0 2308 232500 201928 6976628 0 0 96 296 495 484 4
0 95 0
0 1 2308 232492 201928 6976628 0 0 0 176 347 278 1
0 99 0
0 0 2308 233484 201928 6976596 0 0 40 580 443 351 8
2 90 0
1 0 2308 233484 201928 6976696 0 0 76 692 792 651 9
2 88 0
0 0 2308 233484 201928 6976696 0 0 0 20 132 34 0
0 100 0
0 0 2308 233484 201928 6976696 0 0 0 76 177 90 0
0 100 0
0 1 2308 233484 201928 6976696 0 0 0 216 321 250 4
0 96 0
0 0 2308 233484 201928 6976696 0 0 0 116 417 240 8
0 92 0
0 0 2308 233484 201928 6976784 0 0 48 600 403 270 8
0 92 0
0 0 2308 233464 201928 6976860 0 0 76 452 1064 2611 14
1 84 0
0 0 2308 233460 201932 6976900 0 0 32 256 587 587 12
1 87 0
0 0 2308 233460 201932 6976932 0 0 32 188 379 287 5
0 94 0
0 0 2308 233460 201932 6976932 0 0 0 0 103 8 0
0 100 0
0 0 2308 233460 201932 6976932 0 0 0 0 102 14 0
0 100 0
0 1 2308 233444 201948 6976932 0 0 0 348 300 180 1
0 99 0
1 0 2308 233424 201948 6976948 0 0 16 380 739 906 4
2 93 0
0 0 2308 233424 201948 6977032 0 0 68 260 724 987 7
0 92 0
0 0 2308 231924 201948 6977128 0 0 96 344 1130 753 11
1 88 0
1 0 2308 231924 201948 6977248 0 0 112 324 687 628 3
0 97 0
0 0 2308 231924 201948 6977248 0 0 0 192 575 430 5
0 95 0
1 0 2308 231924 201948 6977248 0 0 0 264 208 124 0
0 100 0
0 0 2308 231924 201948 6977264 0 0 16 272 380 230 3
2 95 0
0 0 2308 231924 201948 6977264 0 0 0 0 104 8 0
0 100 0
0 0 2308 231924 201948 6977264 0 0 0 48 258 92 1
0 99 0
0 0 2308 231816 201948 6977484 0 0 212 268 456 384 2
0 98 0
0 0 2308 231816 201948 6977484 0 0 0 88 453 770 0
0 99 0
0 0 2308 231452 201948 6977680 0 0 196 476 615 676 5
0 94 0
0 0 2308 231452 201948 6977680 0 0 0 228 431 400 2
0 98 0
0 0 2308 231452 201948 6977680 0 0 0 0 237 58 3
0 97 0
0 0 2308 231448 201952 6977680 0 0 0 0 365 84 2
0 97 0
0 0 2308 231448 201952 6977680 0 0 0 40 246 108 1
0 99 0
0 0 2308 231448 201952 6977776 0 0 96 352 606 1026 4
2 94 0
0 0 2308 231448 201952 6977776 0 0 0 240 295 266 5
0 95 0