A Drupal 7 site with CiviCRM, after running smoothly for a year on a 1&1 VPS suddenly became unresponsive. Now pages eventually load, but can take more than a minute.

Looking at resource use in Virtuozzo, the load average carries a warning, and has remained above 1. While I understand this isn't particularly high, this is a change from when the site was working. Here is a typical snapshot of top:

top - 03:10:32 up  3:21,  1 user,  load average: 1.16, 1.22, 1.30
Tasks:  43 total,   1 running,  42 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.1%us,  0.1%sy,  0.1%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   2097152k total,  1015112k used,  1082040k free,        0k buffers
Swap:        0k total,        0k used,        0k free,        0k cached

CPU idle level never seems to go much below 70%. wa is virtually always at 0. There appears to be lots of free memory. And here is some vmstat output, again showign wa at 0, plenty of free memory, and an idle CPU:

procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
2  0      0 1100872      0      0    0    0  2783 23672    0  538  1  0 99  0  0
1  0      0 1100872      0      0    0    0     0    16    0 101754  0  0 100  0  0
0  0      0 1100872      0      0    0    0     0    17    0 103133  0  0 100  0  0
0  0      0 1100872      0      0    0    0     0     1    0 102080  0  0 100  0  0
1  0      0 1100872      0      0    0    0     0     6    0 99881  0  0 100  0  0
0  0      0 1100872      0      0    0    0     0     1    0 105187  0  0 100  0  0

I've spoken to 1&1 but they don't have any ideas as to what could be causing the high load average. Instead they suggested an upgrade :)

I've looked for processes that might be causing this, examined MySQL showprocesslist, and restarted the container with no result. Does anyone have more troubleshooting suggestions or insights?