Monday, 1 June 2015

Quickstart guide to using and interpreting ESXTOP

I have pulled together a quick and dirty guide to capturing and interpreting ESXTOP results.

Launching ESXTOP

ESXTOP can be launched from the command line by ssh'ing into the ESXI host:
esxtop
Metrics and Thresholds

Display Metric Threshold Explanation
CPU %RDY 10 Overprovisioning of vCPUs, excessive usage of vSMP or a limit(check %MLMTD) has been set. See Jason’s explanation for vSMP VMs
CPU %CSTP 3 Excessive usage of vSMP. Decrease amount of vCPUs for this particular VM. This should lead to increased scheduling opportunities.
CPU %SYS 20 The percentage of time spent by system services on behalf of the world. Most likely caused by high IO VM. Check other metrics and VM for possible root cause
CPU %MLMTD 0 The percentage of time the vCPU was ready to run but deliberately wasn’t scheduled because that would violate the “CPU limit” settings. If larger than 0 the world is being throttled due to the limit on CPU.
CPU %SWPWT 5 VM waiting on swapped pages to be read from disk. Possible cause: Memory overcommitment.
MEM MCTLSZ 1 If larger than 0 host is forcing VMs to inflate balloon driver to reclaim memory as host is overcommited.
MEM SWCUR 1 If larger than 0 host has swapped memory pages in the past. Possible cause: Overcommitment.
MEM SWR/s 1 If larger than 0 host is actively reading from swap(vswp). Possible cause: Excessive memory overcommitment.
MEM SWW/s 1 If larger than 0 host is actively writing to swap(vswp). Possible cause: Excessive memory overcommitment.
MEM CACHEUSD 0 If larger than 0 host has compressed memory. Possible cause: Memory overcommitment.
MEM ZIP/s 0 If larger than 0 host is actively compressing memory. Possible cause: Memory overcommitment.
MEM UNZIP/s 0 If larger than 0 host has accessing compressed memory. Possible cause: Previously host was overcommited on memory.
MEM N%L 80 If less than 80 VM experiences poor NUMA locality. If a VM has a memory size greater than the amount of memory local to each processor, the ESX scheduler does not attempt to use NUMA optimizations for that VM and “remotely” uses memory via “interconnect”. Check “GST_ND(X)” to find out which NUMA nodes are used.
NETWORK %DRPTX 1 Dropped packets transmitted, hardware overworked. Possible cause: very high network utilization
NETWORK %DRPRX 1 Dropped packets received, hardware overworked. Possible cause: very high network utilization
DISK GAVG 25 Look at “DAVG” and “KAVG” as the sum of both is GAVG.
DISK DAVG 25 Disk latency most likely to be caused by array.
DISK KAVG 2 Disk latency caused by the VMkernel, high KAVG usually means queuing. Check “QUED”.
DISK QUED 1 Queue maxed out. Possibly queue depth set to low. Check with array vendor for optimal queue depth value.
DISK ABRTS/s 1 Aborts issued by guest(VM) because storage is not responding. For Windows VMs this happens after 60 seconds by default. Can be caused for instance when paths failed or array is not accepting any IO for whatever reason.
DISK RESETS/s 1 The number of commands reset per second.
DISK CONS/s 20 SCSI Reservation Conflicts per second. If many SCSI Reservation Conflicts occur performance could be degraded due to the lock on the VMFS.
%VMWAIT: Is a derivitive of %WAIT and reperesents just the hardware and SWAP waiting time and hence is a better metric to use than %WAIT when diagnosing performance issues such as storage controllers etc.

%WAIT: Reperesents the waiting time for devices (e.g. storage controller), SWAP waiting time AND %IDLE time - so should not be taken at face value!

%RUN: Reperesents the percentage of total time scheduled for the world to run. %USED = %RUN + %SYS – %OVRLP. When the %RUN value of a virtual machine is high, it means the VM is using a lot of CPU resource.

ESXTOP Toggles

c = cpu
m = memory
n = network
i = interrupts
d = disk adapter
u = disk device (includes NFS as of 4.0 Update 2)
v = disk VM
p = power states

V = only show virtual machine worlds
e = Expand/Rollup CPU statistics, show details of all worlds associated with group (GID)
k = kill world, for tech support purposes only!
l  = limit display to a single group (GID), enables you to focus on one VM
# = limiting the number of entitites, for instance the top 5

2 = highlight a row, moving down
8 = highlight a row, moving up
4 = remove selected row from view
e = statistics broken down per world
6 = statistics broken down per world

Exporting results from ESXTOP

From the command line we can run:

esxtop -b -d 2 -n 250 > esxtopout.csv

Interpreting results from ESXTOP

You can directly hook into ESXTOP with a utility called VisualESXTOP (rather than having to manually export it's results - that will build pretty graphs to help you interpet the data a little easier.

References

http://www.yellow-bricks.com/esxtop/
https://communities.vmware.com/docs/DOC-11812
http://buildvirtual.net/analyzing-esxtop-data/

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