https://forums.aws.amazon.com/thread.jspa?messageID=242262𻉖
AWS oversubscribes instances like all cloud providers. You can track this in Linux distribution vmstat command there is a new CPU st%, see vmstat man page:
CPU
These are percentages of total CPU time.
us: Time spent running non-kernel code. (user time, including nice time)
sy: Time spent running kernel code. (system time)
id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
wa: Time spent waiting for IO. Prior to Linux 2.5.41, included in idle.
st: Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown.
I keep performance stats on every Linux machine and log this, when I checked stolen CPU I found significant "noisy neighbors":
cat */vmstat.out | grep -v cache | awk ' { print $20 " - " $0 } ' | sort -nk1 | tail -20
67 - 9 0 9.00 69 0 0 572220 18092 85776 0 0 1 13 157 277 29 4 0 0 67 33
67 - 9 12 9.20 58 0 0 361924 20460 536836 0 0 1 35 143 918 25 8 0 0 67 33
67 - 9 18 9.30 51 0 0 833732 24444 194828 0 0 1 21 145 546 26 6 0 0 67 32
67 - 9 18 9.30 61 0 0 561168 20328 87748 0 0 1 20 156 369 28 4 0 0 67 32
67 - 9 24 9.40 41 0 0 966656 38212 125780 0 0 0 19 149 497 28 5 0 0 67 33
67 - 9 24 9.40 59 0 0 443368 21620 541624 0 0 1 27 151 879 27 6 0 0 67 33
67 - 9 30 9.50 58 0 0 870608 25784 195864 0 0 1 27 142 754 26 7 0 0 67 33
67 - 9 30 9.50 68 0 0 200180 22220 541308 0 0 0 22 150 1282 27 6 0 0 67 33
67 - 9 30 9.50 69 0 0 549048 21464 87980 0 0 0 19 152 367 28 5 0 0 67 33
67 - 9 36 9.60 48 0 0 809492 39184 124840 0 0 0 23 153 434 27 5 0 0 67 32
67 - 9 42 9.70 64 0 0 304240 23456 364808 0 0 0 28 149 1232 27 6 0 0 67 33
67 - 9 48 9.80 51 0 0 849336 27572 199396 0 0 0 27 149 509 26 6 0 0 67 32
67 - 9 48 9.80 62 0 0 641024 23152 89536 0 0 1 23 148 471 27 5 0 0 67 32
67 - 9 54 9.90 38 0 0 675652 40736 126008 0 0 0 16 150 313 28 4 0 0 67 32
67 - 9 54 9.90 57 0 0 293160 24588 366064 0 0 0 22 155 773 28 5 0 0 67 33
67 - 9 6 9.10 42 0 0 916620 36724 125800 0 0 0 20 150 340 28 5 0 0 67 33
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