ESXTOP

Intro
Thresholds
Howto – Run
Howto – Capture
Howto – Analyze
Howto – Limit esxtop to specific VMs
References
Changelog
This page is solely dedicated to one of the best tools in the world for ESX; esxtop.

Intro

I am a huge fan of esxtop! I read a couple of pages of the esxtop bible every day before I go to bed. Something I however am always struggling with is the “thresholds” of specific metrics. I fully understand that it is not black/white, performance is the perception of a user in the end.
There must be a certain threshold however. For instance it must be safe to say that when %RDY constantly exceeds the value of 20 it is very likely that the VM responds sluggish. I want to use this article to “define” these thresholds, but I need your help. There are many people reading these articles, together we must know at least a dozen metrics lets collect and document them with possible causes if known.
Please keep in mind that these should only be used as a guideline when doing performance troubleshooting! Also be aware that some metrics are not part of the default view. You can add fields to an esxtop view by clicking “f” on followed by the corresponding character.
I used VMworld presentations, VMware whitepapers, VMware documentation, VMTN Topics and of course my own experience as a source and these are the metrics and thresholds I came up with so far. Please comment and help build the main source for esxtop thresholds.

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.

Running esxtop

Although understanding all the metrics esxtop provides seem to be impossible using esxtop is fairly simple. When you get the hang of it you will notice yourself staring at the metrics/thresholds more often than ever. The following keys are the ones I use the most.
Open console session or ssh to ESX(i) and type:

esxtop

By default the screen will be refreshed every 5 seconds, change this by typing:

s 2

Changing views is easy type the following keys for the associated views:

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

Add/Remove fields:

f
<type appropriate character>

Changing the order:

o
<move field by typing appropriate character uppercase = left, lowercase = right>

Saving all the settings you’ve changed:

W

Keep in mind that when you don’t change the file-name it will be saved and used as default settings.
Help:

?

In very large environments esxtop can high CPU utilization due to the amount of data that will need to be gathered and calculations that will need to be done. If CPU appears to highly utilized due to the amount of entities (VMs / LUNs etc) a command line option can be used which locks specific entities and keeps esxtop from gathering specific info to limit the amount of CPU power needed:

esxtop -l

More info about this command line option can be found here.

Capturing esxtop results

First things first. Make sure you only capture relevant info. Ditch the metrics you don’t need. In other words run esxtop and remove/add(f) the fields you don’t actually need or do need! When you are finished make sure to write(W) the configuration to disk. You can either write it to the default config file(esxtop4rc) or write the configuration to a new file.
Now that you have configured esxtop as needed run it in batch mode and save the results to a .csv file:

esxtop -b -d 2 -n 100 > esxtopcapture.csv

Where “-b” stands for batch mode, “-d 2″ is a delay of 2 seconds and “-n 100″ are 100 iterations. In this specific case esxtop will log all metrics for 200 seconds. If you want to record all metrics make sure to add “-a” to your string.
Or what about directly zipping the output as well? These .csv can grow fast and by zipping it a lot of precious diskspace can be saved!

esxtop -b -a -d 2 -n 100 | gzip -9c > esxtopoutput.csv.gz

Please note that when a new VM is powered on, a VM is vMotion to the host or a new world is created it will not show up within esxtop when “-b” is used as the entities are locked! This behavior is similar to starting esxtop with “-l”.

Analyzing results

You can use multiple tools to analyze the captured data.

1. VisualEsxtop
2. perfmon
3. excel
4. esxplot