What t1.micro CPU Bursting Looks Like

Amazon’s smallest and least expensive instance type, the t1.micro “provide[s] a small amount of consistent CPU resources and allow[s] you to burst CPU capacity when additional cycles are available. [It is] well suited for lower throughput applications and web sites that consume significant compute cycles periodically.” (source)

Running a cpu-bound workload (building Perl modules) on an Ubuntu 11.10 t1.micro instance in us-west-2 tonight, I noticed the following curious CPU usage pattern of approximately 15 seconds on, 60 seconds off:

> vmstat 5
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 1  0      0  38528  29524 370540    0    0    86   423   84  216 12  5 35  4
 1  0      0   6800  30288 388856    0    0  5356    26  660 1433 27 27  6 40
 5  0      0  21752  27624 378088    0    0    30   211  150  159 40 22  0  8
 6  0      0  21256  27636 378104    0    0     0    27    9    7  1  1  0  0
 7  0      0  21256  27644 378108    0    0     0    10    9    9  1  1  0  0
 7  0      0  21256  27652 378112    0    0     0     8    9    9  2  1  0  0
 7  0      0  20256  27652 378228    0    0     0     0    8   13  1  1  0  0
 8  0      0  20016  27660 378072    0    0     0   218   15   29  0  2  0  3
 6  0      0  37884  27672 378048    0    0     0    14    9   11  3  1  0  0
 4  0      0  30808  27684 378048    0    0     0    11    9   10  1  1  0  0
 4  0      0  23740  27692 378056    0    0     0    10    8    8  2  1  0  0
 4  0      0  30676  27692 378104    0    0     0     0   10   10  1  1  0  0
 5  0      0  26220  27700 378064    0    0     0     9    7   14  6  2  0  1
 5  0      0  21012  27712 378120    0    0     0    10    9   10  1  0  0  0
 5  0      0  27336  27720 378064    0    0     0    21   13   10  1  1  0  0
 1  0      0  29444  27732 378064    0    0     0    14  149   97 39 19  0  0
 1  0      0  33420  27744 378084    0    0     6    12  250  166 67 30  0  0
 2  0      0  41108  27756 378100    0    0     0    37  207  148 60 29  0  0
 6  0      0  33668  27768 378068    0    0     0    14    8    9  1  1  0  0
 5  0      0  37008  27780 378068    0    0     0    10   10   15  4  1  0  0
 4  0      0  30808  27788 378072    0    0     0    18   11    9  2  0  0  0
 5  0      0  24360  27796 378092    0    0     0     9    8    7  2  0  0  0
 2  0      0  19896  27796 378140    0    0     0     0    8    9  1  1  0  0
 6  0      0  27584  27804 378152    0    0     0     7    8   12  1  1  0  0
 6  0      0  22864  27812 378148    0    0     0     9   10   12  2  1  0  0
 7  0      0  19136  27820 378152    0    0     0    10    8    9  1  1  0  0
 6  0      0  26096  27828 378148    0    0     0    12   10    7  2  1  0  0
 6  0      0  20640  27828 378156    0    0     0    19   13    8  2  1  0  0
 6  0      0  27956  27836 378156    0    0     0    11    9   12  1  1  0  0
 6  0      0  22864  27844 378156    0    0     0     6    9   12  2  1  0  0
 6  0      0  19020  27844 378156    0    0     0     1    9    9  1  1  0  0
 2  0      0  46896  21504 368588    0    0   518    18  261  291 47 29  1  7
 1  0      0  35372  21692 368788    0    0     0    43  253  174 65 32  0  0
 1  0      0  43060  21796 368600    0    0     0    62  149  112 66 32  0  1
 5  0      0  38100  21808 368600    0    0     0    46   11   10  1  1  0  0
 5  0      0  45788  21816 368592    0    0     0     7    8   12  2  1  0  0
 7  0      0  38464  21816 368600    0    0     0     0    7    8  2  1  0  0
 7  0      0  45912  21824 368596    0    0     0    11    9    9  2  1  0  0
 7  0      0  39216  21832 368600    0    0     0     7    9    8  1  0  0  0
 4  0      0  35496  21840 368596    0    0     0    19   11    9  4  1  0  0
 5  0      0  43060  21848 368600    0    0     0    29   10   10  2  1  0  0
 5  0      0  37480  21856 368592    0    0     0    11    9   10  1  1  0  0
 5  0      0  45044  21864 368596    0    0     0     7    9   10  1  1  0  0
 5  0      0  38340  21872 368600    0    0     0     8    8    8  2  1  0  0
 4  0      0  46284  21880 368596    0    0     0    10   10   11  1  1  0  0
 6  0      0  38836  21888 368592    0    0     0     8    8    8  2  1  0  0
 1  0      0  38340  21888 368544    0    0     0    15   53   41 12  7  0  0
 1  0      0  40828  21900 368568    0    0     2    46  255  218 66 33  0  0
 1  0      0  39960  21912 368608    0    0     0    26  237  153 63 28  0  0
 3  0      0  50632  21924 368540    0    0     0    16   58   44 32 15  0  0
 4  0      0  46284  21932 368540    0    0     0     7    8   11  1  1  0  0
 4  0      0  45400  21940 368540    0    0     0     6    9   10  1  1  0  0
 5  0      0  45292  21948 368552    0    0     0    11    8   14  0  1  0  0
 6  0      0  37720  21948 368584    0    0     0    17   12    6  2  1  0  0

Apparently, the “small amount of consistent CPU resources” is about 3% of the CPU.

Moral of the story for me? Next time, pay the big bucks and launch an m1.small spot instance.

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