XenApp

Citrix XenApp, OpenGL pass-through and Nvidia GRID cards on Amazon EC2 (G2 Instances)

2015-09-01
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I’m attempting to do a Proof of Concept (POC) for a client and one of the ideas was to utilize the Amazon EC2 cloud to provide GPU instances to the users for their applications (Maya, SolidWorks, etc.).  In order to understand how GPU sharing works, I setup my home lab to take advantage of these features first, in order to understand how it operates.

Citrix provides documentation on setting up the GPU sharing.  For my test, I’m doing this on a bare metal Citrix server.  Essentially, the notes state that OpenGL is automatically shared and enabled and special steps must be taken for DirectX, OpenCL, CUDA and Windows Server 2012.  To enable GPU sharing for XenApp for these features, the following registry file will enable these:

Windows Registry Editor Version 5.00
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\CtxHook\AppInit_Dlls\Graphics Helper] “DirectX”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\CtxHook\AppInit_Dlls\Graphics Helper] “DirectX”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\CtxHook\AppInit_Dlls\Multiple Monitor Hook] “EnableWPFHook”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\CtxHook\AppInit_Dlls\Multiple Monitor Hook] “EnableWPFHook”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\CtxHook\AppInit_Dlls\Graphics Helper] “CUDA”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\CtxHook\AppInit_Dlls\Graphics Helper] “CUDA”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\CtxHook\AppInit_Dlls\Graphics Helper] “OpenCL”=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\CtxHook\AppInit_Dlls\Graphics Helper] “OpenCL”=dword:00000001

In addition to this registry file, for Server 2012, the following Group Policy object is required:

  • On Windows Server 2012, Remote Desktop Services (RDS) sessions on the RD Session Host server use the Microsoft Basic Render Driver as the default adapter. To use the GPU in RDS sessions on Windows Server 2012, enable the Use the hardware default graphics adapter for all Remote Desktop Services sessions setting in the group policy Local Computer Policy > Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Remote Session Environment.

My initial setup is a Q87M-E system with a Intel 4771 and onboard graphics.  My system is setup with Windows 2012 R2 with Citrix XenApp 7.6.

Launching an ICA session to the XenApp 7.6 server results in:

 

 

We have OpenGL working, DirectX 11, and OpenCL (the onboard Intel GPU’s do not support CUDA).  So we have a full, working implementation of GPU sharing in a ICA session on a XenApp server.

But the onboard Intel graphics card will not get the me the performance I want.  I had a Nvidia GTX 670 video card on hand to see if I can get better 3D performance.  I installed that card in the system, installed the video drivers and checked the results.

 

Where did my OpenGL go?  Everything else is working correctly; Direct3D, CUDA, OpenCL, but not OpenGL.  My understanding from Nvidia is that OpenGL should just be ‘passed through’ by Citrix.  I know that it *does* pass-through because we, literally, just saw it with the onboard Intel GPU and the Intel drivers.

My next thought is maybe it had to do with the drivers?  Maybe if I tried the Quadro drivers?  It turns out Nvidia has released special Quadro drivers that enable OpenGL in a RDP session. Maybe if I modified the INF to add my GTX670 to these special drivers I could get OpenGL to work?

 

It did not work.  OpenGL remained disabled in RDP/ICA sessions.

Suspecting Nvidia is doing some form of detection that is disabling OpenGL (it’s probably considered a ‘pro’-feature) I acquired a Quadro FX5800 and using the *same* modified Quadro drivers, these were my results:

 

OpenGL is now working!!

Ok, so, at this point I know how to enable GPU sharing for Citrix XenApp, I know how to check and verify it’s functionality, and I know that different Nvidia cards can have OpenGL enabled or disabled but am not sure if it’s the driver that matters or the hardware.  If it’s the hardware I’m a bit surprised Intel would incorporate hardware accelerated OpenGL into ICA sessions for their consumer pieces but Nvidia would not for their discrete cards.  To *attempt* to test this I went and got the oldest driver I could find that would support a FX5800:

Sure enough, it works.

My last thought is maybe Nvidia has it hard coded somewhere to check for a string or a specific ‘type’ of video card and, if found, enable OpenGL?

My thinking is that the Nvidia drivers are doing some kind of detection and making a determination between a console session and all others.  If I’m lucky, maybe they only implemented this in their *newer* drivers, maybe after they started the RDS OpenGL acceleration…

To test this theory I went and grabbed the oldest driver I could find for my GTX 670 that would work on Windows 2012R2.  327.23.

 

Well now…  OpenGL is working.  This is interesting.  And leads evidence that OpenGL is being disabled in ICA via the driver.  I attempted to find when OpenGL *stopped* working.

331.82 –> Works, and now with OpenGL 4.4

337.88  -> Works

340.52 -> No OpenGL.  This driver (340.52) is now the first gaming driver *After* the “OpenGL on RDS release” (340.43).  It appears something on or after the 340.XX branch is disabling OpenGL in ICA sessions.

At the same time I was testing my Nvidia gaming GPU on my home lab, I was testing Amazon.  The GPU instance that Amazon provides utilize the Nvidia GRID K520 card as a vGPU.  This card is marketed as a ‘GRID Gaming‘ card.  I setup this instance with Citrix XenApp and, at the time, used the latest driver (347.70).  At the time of this testing, this was my 3rd rebuild of this instance so I went with Server 2008 because my previous 2 builds were 2012 and I was convinced I was doing something wrong.  The OS shouldn’t matter, but I’m noting it here.

347.70 –> No OpenGL (just like the gaming card):

Knowing that downgrading the gaming card’s driver worked, I installed the oldest driver I could for the K520:

320.59 –> OpenGL Works!

Just like the gaming card.  I suspect the K520 will have the same issue as the GTX 670, and that any driver after 340.XX will disable OpenGL in a ICA session.  Unfortunately, the Grid K520 appears to only have 3 drivers to chose from, 320.59, 335.35, and 347.70.  To finish this testing I will test with 335.35:

OpenGL Works!  So it appears driver 340 and newer will disable OpenGL for ICA sessions across various types of Nvidia GPU’s, but not Quadro’s..

If you want OpenGL to work on Amazon EC2 instances, you must (at the time of this writing…  hopefully Nvidia corrects this over sight for all cards – consumer and not) you must use a driver older than 340.

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Citrix Seamless Flags and their impact

2015-07-23
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While investigating a performance issue with an application in our Citrix farm a curiosity was discovered when someone opened up Process Explorer and found the CPU utilization on the server was much higher than expected or reported by various monitoring tools we use.

Examining what was utilizing the CPU we found the process ‘winlogon.exe’ was consuming nearly the entire difference between Process Explorer and Task Manager.

Process Explorer allows us to dive ‘deeper’ into the process to determine the thread that is utilizing our CPU.
twi3.dll is a Citrix file.  Click ‘Module’ and getting properties gives us more information about the file and its purpose.

“Seamless 2.0 Host Agent – main component”


 Now that we have an idea of the purpose of twi3.dll is, we can being to test why it’s consuming so much CPU.  Citrix has options for modifying the behaviour of twi3.dll via “Seamless Flags”.
For our environment we had the following set:
I experimented with modifying each value to determine what the impact on the CPU on the twi3.dll threads would experience.
To that end, you can modify these values immediately and they take effect on the next session connect (but does not impact existing sessions).  With that, here were my results:
Lower numbers for CPU% are better and per user.  More CPU’s actually lower the maximum % winlogon.exe can consume, for this test it was done with a 6 core CPU.  Less CPU’s and the maximum % increases..  I imagine this is due to a thread limit or some such?  
The values that had the most impact on CPU utilization were the lowest values for the WorkerWaitInterval or WorkerFullCheckInterval followed by Disable Active Accessibility Hook.
So what does WorkerWaitInterval / WorkerFullCheckInterval do?
WORKER WAIT INTERVAL / WORKER FULL CHECK INTERVAL
Explanation: This update addresses a custom application’s performance when run seamlessly. Some applications appeared to be slower to respond when performing actions such as moving, resizing, or closing windows. This fix introduces two new registry settings that allow administrators to configure an explicit time interval for the seamless engine mechanism to monitor when changes take place in the seamless applications.

For both values, a larger size slows responsiveness but improves scalability; a smaller size increases responsiveness but decreases scalability slightly. The level of scalability depends on several factors, such as hardware sizing, types of applications, network performance, and number of users. 

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlCitrixwfshellTWI Value Name: WorkerWaitInterval
Type: REG_DWORD
Value: 0
Value: (Values are between 5 – 500; the default is 50.)

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlCitrixwfshellTWI Value Name: WorkerFullCheckInterval
Type: REG_DWORD
Value: (Values are between 50 – 5000; the default is 500.)

For the graph above, the WorkerWaitInterval and WorkerFullCheckInterval defined in milliseconds, when they are a low value, forces the seamless engine to monitor for changes at a higher pace.  This consumes additional CPU cycles.  
For our environment we encountered issues as user count increased.  It turns out, as each user logged on they consumed a fairly constant amount of CPU.  The winlogon.exe process for the server in the screenshot averaged around 0.8% CPU per user, with 35 users that’s 28% of the CPU no longer available.  So why does Task Manager not display these values?  The author of Process Explorer has the answer:
The configured time range we configured were 5ms so the threads executing have a good chance being before or after the timer tick of 15.6ms.
So this poses a question of what *should* the values be?  Citrix Adaptive Display technology has a maximum frame rate of 30 for XenApp 6.5 and a maximum of 60 for XenApp 7+.  Potentially, I think to achieve these frame rates a value of 16 for XA7 or 33 for XA65 could be set.  If the FPS is set to a lower maximum, it would probably make more sense to do the math for that maximum FPS?
Further testing may be needed here.

Lastly, if you do not use Seamless Flags, e.g., if you use Shift F1 to switch to Window’ed Mode then Winlogon.exe will use no CPU for twi3.dll.  You also get the same results with RDP, no CPU being used.

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Citrix PVS Target Device Update script

2015-03-20
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Saman and I have created a Citrix PVS update script we use and run each time we update a PVS target device.  This script has been generated after finding numerous issues that needed to be fixed after updating a PVS image.  It includes fixes to issues with AppV5, PVS, XenApp 6.5, etc.

We also made the script to be able to be run automatically by accepting command-line parameters so that we can use it to do Windows Updates with PVS’s automatic vDisk update feature.

I’ve removed email addresses and some specific application fixes that would only be relevant to our environment.  So I’ve tried to generalize this the best I can.  We tried to make this script dynamic so if you have a vDisk without AppV it will skip the features that require AppV, skip 64bit only features, etc.

I will post the supplemental scripts in more posts.

 

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Exploring the Citrix XML 6.5 Broker in more detail

2014-11-28
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The Citrix XML broker actually relies on many pieces to ensure fast and proper operation. This CTX article describes the process for XenApp 6 (seems applicable to 6.5 as well).

The part that is relevant to the XML broker is steps 4-9.

4. The user’s credentials are forwarded from XML to the IMA service in HTTP (or HTTPS) form.

5. The IMA then forwards them to the local Lsass.exe.

6. The Lsass.exe encrypts the credentials and passes them to the domain controller.

7. The domain controller returns the SIDs (user’s SID and the list of group SIDs) back to Lsass.exe and to IMA.

8. IMA uses the SIDs to search the Local Host Cache (LHC) for a list of applications and the Worker Group Preference policy for that authenticated user.

9. The list of the applications together with the user’s worker group preference policy are returned to the Web Interface.

So what does this look like (click to blow it up)?

Starting with packet #32 we see the initial POST request for a list of applications.

Steps 5, 6 and 7 are packets 36-86.  LSASS goes back to AD to grab the SID’s.

Step 7.5: It appears that the first time you enumerate applications on a broker that information is queried to the SQL database and stored in the local host cache.  This would be packets 87-94.  Additional queries done do not show this traffic.

Lastly, step 9 is all the traffic we see after packet 95 in red; the return of the XML data.  For our setup, our XML brokers responded with the following timings:

Step 4: 1ms
Step 5: 2ms
Steps 6 and 7: 47ms
Step 7.5 (DB query is not in LHC): 2ms
Step 8: 14ms
Step 9: 14ms

Total: 80ms

With a freshly created LHC this is what process monitor sees:

Again, the IMASrv.exe will actually NOT be present in this list if you have executed at least one query against the XML broker as it is only displayed when it queries the database (wssql011n02) and stores the response in the LHC.

So, what could contribute to slow XML broker performance?

Utilizing the WCAT script we can continuously hammer the XML broker with however many connections we desire.  The XML brokers have a maximum of 16 threads to deal with the incoming traffic but at 80ms per request/response the queue would have to get fairly long to create a noticeable performance impact.  In addition, previous tests on the 4.5 broker showed additional CPU’s help improve the performance of the XML broker, I think the 6.5 broker shows better performance with lesser CPU’s.

Utilizing the bandwidth emulator, clumsy, I’m going to simulate some poor network performance on the XML broker to see what the effects will be of how XML response times will vary.  The only network hits I can see are from the source (Web Interface), Active Directory, and (potentially) the SQL database.

Just starting the clumsy software with it’s filtering by IP capabilities added about 800ms to the total roundtrip time.  Something to consider with other network management/threat protection software I imagine…

Anyways, adding just 20ms of lag to and from the web interface to the XML broker increased processing time by another 500ms of total time.  That is, 1500ms on the low end on 2200 on the high.  Increasing packet latency to 100ms brought the total processing time to 2700ms on the lowend and 3800ms on the high end.  I think it’s safe to say that having the web interface and XML brokers beside each other for the lowest possible latency is a big performance win.

Targeting Active Directory with a latency of 20ms brought times from 420ms to 550ms.  Increasing that to 100ms brought the response times put to 890ms.  Not too shabby.  Seems AD is more resilient to latency.

Targeting the SQL database with a latency of 100ms showed the first query after the LHC was rebuilt went to 600ms and then back down to 420ms there after.  Locality to the database seems to have the lowest impact, but the 100ms lag did increase the LHC rebuild time to about 3 minutes from near instantly before.
I did try to test a heavy disk load against the XML broker but I was running this server with PVS with RAMDisk Cache overflow enabled which means my LHC is stored in RAM and no matter how hard I punted the C:\ drive I couldn’t make an impact.

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Load testing Citrix XML broker

2014-11-27
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Previously, we encountered performance issues with the Citrix Web Interface due to our user load.  I devised a test using the Microsoft WCAT to hammer the web interface servers.  We found that after removing the ASPX processing limitation, logins were slow and we found that some XML brokers were taking a long time to respond.

I’ve been tasked with finding out why.  The Citrix XML server is a basic web server that takes an XML post, processes it and spits back a XML file in response.  To test the performance of the XML server I created a PowerShell script to send the same XML request that occurs when you login through the web interface.

XML-Test.ps1:

 
The list_of_xml.csv looks like this:
Farm,Broker,Port
farm,wsctxrshipxml1,80
The output of the file looks like so:
11/26/2014 3:34:29 PM,wsctxrshipxml1,80,312.197
11/26/2014 3:34:30 PM,wsctxrshipxml1,80,345.0929
11/26/2014 3:34:31 PM,wsctxrshipxml1,80,255.165
11/26/2014 3:34:33 PM,wsctxrshipxml1,80,294.3027
11/26/2014 3:34:34 PM,wsctxrshipxml1,80,300.1806
The times are in milliseconds on the far right.
Utilizing this information, we can gather how quickly the XML brokers respond and using this as a baseline we can start to load test to see the impact of how quickly the XML brokers will respond.
To do this, we go back to WCAT.  I set my XML.ubr file like so:
I then started the
start “” wcclient.exe localhost
And let it roll.  When monitoring the server the process that takes up the most time is the IMASRV.EXE.  I imagine that is because the XML service is really just a simple web server that accepts the traffic and hands it off to the IMASRV.exe to actually process and gets the response back and sends it back to the requestor.
Started load testing at 11:49:00.  After 40 concurrent connections XML service is responding to requests at 2000ms per request.
With this testing we can now try to improve the performance of the XML broker.  We monitored one of our brokers and made some changes to it and reran the test to see the impact.  The largest positive impact we saw was adding CPU’s to the XML brokers.  The following graphs illustrates the differences we saw:

 

I stopped the graph at around 20,000ms for responding to XML request for the top graph, and the maximum number of concurrent connections for the bottom graph at 3,000ms.  3,000ms would be very high for XML enumeration in my humble opinion, but still tolerable.  On a single CPU system, XML enumeration can only sustain about 12-15 concurrent requests before it tops out, 2 CPU systems do slightly better at 24-28 concurrent requests and 4CPU at 60 concurrent requests.  8 CPU’s and we exceed 3,000ms at 120 concurrent requests.  Ideally, you would keep all requests under 1,000ms, which for 8 CPU is at 30 concurrent sessions, and 21 sessions for 4CPU.  1 CPU can only sustain about 2 concurrent requests to stay under 1,000ms while 2 CPU can sustain about 5 concurrent requests.
Again, this is the same query that the web interface sends when you login to a farm.  So if you have 10 farms and they all take 1,000ms to respond to an XML request you will sit at the login screen for 10 seconds.  Storefront allows parallel requests which would reduce the time to 1 second (potentially) but for Web Interface (and even Store Front), having an optimized XML broker configuration is ideal and, apparently, is very dependent on the number of CPU’s you can give it.  Recommendation:
As many as possible.  Unfortunately, I did not have the ability to test 16 or 32 core systems but for an Enterprise environment, I would try to keep it at 8 as a minimum.
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Optimizing Citrix Web Interface 5.4

2014-11-27
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My previous post detailed testing the limits of your Citrix Web Interface.  During this testing we discovered there appeared to be a limit on the number of connections the Citrix Web Interface could accommodate.  This discovery masked the true limitation: the Citrix Web Interface is limited by the number of threads its w3wp.exe process can spawn to handle ASPX pages.  The w3wp.exe process spawn threads to handle the number of connections/load and once it exceeded 48 threads then further requests go into the application queue.  This limitation exists when running a ASP.NET application under ASP.NET 2.0 in Classic mode.  In integrated mode this limitation is determined differently and not applicable.  Unfortunately, the Citrix Web Interface runs in Classic mode under ASP.NET 2.0.

This formula is determined by the number of CPU’s you have times an arbitrary number Microsoft decided would be good for dealing with ASPX pages set back in the IIS 5 or IIS 6 days.  It is woefully low and sadly, Citrix does not resolve it when you install the Web Interface application.

But, we can increase the per processor thread count to prevent the queuing.  To do so you must edit the “C:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG\machine.config” and set the processModel with a new set of thread values.

The values are MaxWorkerThreads, MaxIoThreads, MinWorkerThreads and MinIoThreads.  All values are set * the number of processors you have and are *per w3wp.exe process*.  So if you have a XenApp website and services site running on separate application pools each process then has a 1000 thread limit on a 2 processor system.  When we implement these we found we could hammer the web interface and the ASPX pages would consistently respond without issue.  We did find that hammering the web interface with 1000 threads then revealed a new performance limitation.  Though the ASPX pages were being processed so the explicit login page now constantly appeared without issue, we found that logging in and showing the applications was now slow, taking several dozen seconds at times.  By allowing our web interface to process more connections and pass those connections on; some of our dedicated XML brokers were having issues keeping up with the requests.

My next post will detail testing the capabilities of the XML server and seeing if we can determine the best way to optimize XML performance.

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Slow Citrix Web Interface 5.4 on ASPX pages (or how to load test your WI)

2014-11-23
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We’ve been having issues with our Citrix Web Interface (5.4.2) with it cratering to the point that you cannot even get to the explicit logon page, stuck on SilentDetection.aspx or another aspx page.

One Moment Please…  This screen takes minutes to resolve

So what could be causing this?  More often than not, it’s a broken XML broker that isn’t responding in a reasonable amount of time.  But XML brokers don’t come into play with ‘Explicit Logon’, especially if you can’t even get to the logon page.  In our scenario, we have two production Citrix Web Interface servers which are load-balanced in a round-robin scenario.

So I theorized that what’s happening is we are experiencing a load issue.  That is our server cannot handle the number of connections that we our clients and PNA agents are producing.  How can we prove this out?  How many connections can our web interface accept?

To test out what the maximum number of connections our web interface servers can sustain I came up with a plan.  We need to thoroughly exercise the ASP.NET scripts that Citrix has put together for the web interface.  To do that we need I decided that logging in via explicit logon, skipping client installation (so client detection occurs) and then application enumeration.  This sequence hits the following ASPX pages:

 

The timeline of processing the aspx pages of a unloaded server looks like this:
The initial silentDetection.aspx’s take the majority of the processing time, about 4.3 seconds.  To create the ability to simulate this load, Microsoft has a tool called “WCAT”, or the Web Capacity Analysis Tool.  This tool allows you to setup “scenario’s” which are a sequence of HTTP actions (GET/POST/etc) which simulates each step of the sequence above.  To record this sequence for WCAT, you need to install Fiddler 2 then install the WCAT scenario creator.  There are numerous WCAT scenario creators, but I used this one.  To create the scenario do the following:
1) Launch Fiddler 2 and click ‘Launch’
2) Go through your login sequence on your web server until you hit the page with application enumerations.

 

 

3) Go back to Fiddler 2 and at the bottom of the screen on the left in the black bar, type “wcat reset”
4) Go Edit > Select All.  Then in the black bar, type ‘wcat addtrans’
5) Lastly, type ‘wcat save’.
This will create a fiddler.wcat file in your C:Program Files (x86)Fiddler2 directory.
You can now open this file as a text file to see the scenario you just created.  One of the issues with this WCAT scenario creator you will need to fix up some cookie values.  Some cookie values are captured exactly as described, which has some issues as double quotes need to be escaped in the scenario file.
So, for example, this line:
Won’t work.  You need to escape out the double-quotes with a back-slash so it looks like so (the backslashes are bolded and underlined):
Once you’ve escape’d the double quotes, save the file as ‘scenario.ubr’; you can now setup WCAT.
Install WCAT on some test boxes or a single box (for the purposes of this demo I’m doing just a single box).
Copy over your scenario.ubr to the C:Program Fileswcat folder.  I took the settings.ubr file from the Samples directory in the wcat folder and put it in the root of the wcat folder as well.
You then need to start the controller and attach clients to this server.  Open a command prompt to the wcat directory.  The command line I used for the controller is:
wcctl -t scenario.ubr -f settings.ubr -s wsctxwi01t -c 20 -v 20 -w 300 -u 300 -n 100
the values are:
-c = # of clients to connect to this controller.
-v = # of virtual clients to launch per client
-w = warm up time before all clients are connected
-u = duration of testing
-n = cooldown period for clients to disconnect.
Since I’m testing from one computer I then used the following command to start all my clients:
for /l %A IN (1,1,20) do (start “” wcclient.exe localhost)
The 20 clients connect and start loading the server, following the sequence we recorded earlier.
If you want to monitor to see where your maximum user load is vs. maximum performance (e.g., near instant speed), go to your web interface server and create a data collector set with the following counters:
Without any clients connected, start your data collector, then start the WCAT load testing.
This is what I see with regards to our load:
You can see around 220 current connections the Requests in Application Queue shoots up.  At this point any additional requests to ASPX files goes into a queue that makes the website appear ‘frozen’ which it waits for the ASPX file to be processed and sent down to you.  Citrix attempts to ‘hide’ this page by loading the ‘loading.htm’ during ASPX processing.  This page is your ‘One Moment Please’ page.  If you show the Request Execution Time counter, we can see the longest time taken to process a ASPX page:

 

In my example here, the longest time it took to process a ASPX page was is the lighter pink line.  The longest time was 14 seconds.
The Request Wait Time is how long it takes of while you wait in the queue for the ASPX page to be processed.  So the dark blue line with the spike in the bottom right was a 16 second wait time, waiting for my page to start processing, and with the request execution time being 14 seconds this particular request may have taken 30 seconds in total.
With this information we can fairly accurately determine that we would want to keep the number of current connections to around or under 150 just to keep a safe buffer.  To do that, we could increase the number of web interface servers or break out our web server to different Application Pools.  Our Citrix web interface was originally designed with a monolithic application pool and our PNA website and other websites all run under one process.  In our situation, we could exceed our connection limit during times when Citrix Receiver checks in to enumerate applications at the same time as users trying to use the web site.  If we break the PNA website to a new application pool then we can actually double the number of connections we can process at any one time.  The limit appears to be the w3wp.exe ability to process ASPX pages.  By adding another application pool it actually creates another w3wp.exe process and if we max out the connections on one of the websites the other website/process will continue to work without issue.
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Unable to launch /appvve switch via XenApp 6.5

2014-10-16
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It appears you can’t launch an AppV environment around an application with the /appvve switch as Microsoft automatically strips the /appvve switch OR because icast.exe freaks out.

I have found an alternative method though:

This will launch a cmd.exe window in the virtual environment in citrix with the passed .exe (cmd.exe in this example).

Dan mentioned another, less character way:

 

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Quick Hit – ICA-TCP#0 and disconnected sessions

2014-09-26
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If you were to login to a Citrix server with your ID and you get ICA-TCP#0 as your session name, then disconnected your session, went to another computer and logged in (in the Metavision environment you don’t assume the exisiting session — you get a new one) you will actually take that sessionName “ICA-TCP#0” as the disconnected session made it available. If you reconnect to your disconnected session it will update the SessionName variable to ICA-TCP#1.

I bring this up because I was attempting to use this variable in the registry to determine a user’s process list but it fails because of the disconnected session maintaining that same value.

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Citrix, Internet Explorer and AppV

2014-04-24
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I wrote about the issue of Internet Explorer and AppV here before.  Long story short, Citrix changes the iexplorer.exe launch handle to point to its own stub of iexplore.exe.  I suggested changing the iexplore in the registry to point to the proper version of IE, but the Citrix version appears to be a FTA (File Type Association) stub of some sort.  Another solution would be to use the full path to iexplorer.exe (C:\Program Files (x86)\Internet Explorer\iexplore.exe) in the path of the published Citrix application.  This avoids the stub being launched.

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