Re: QShell performance -- MIDRANGE-L

Ok, I've checked on my own system with V7R1. This is a Power7 with just 2 virtual disks, 0.5 CPU LPAR and VIOS.

I changed my DNS to *LOCAL and a non-existing server. QSHELL performance goes down, but just 1 second or 2 with "ls" or "hostname" commands.

Then changed my DNS to *REMOTE and the same no-existing server. QSHELL performance goes to 10 seconds and even more with "ls" and "hostname" commands.

I have all the hostnames entries on CFGTCP + 10 option.

Regards

Diego E. KESSELMAN

El 20/06/17 a las 10:02, Scott Klement escribió:

Diego,

What were you doing in QShell that didn't perform well when hostname was a mess? I've seen this too, but it was under specific situations where a program connected to the local system via Java classes.

You might think "it's the local system, why would networking even apply" -- it applies because it's necessary to connect to network servers to do things like call native programs, run SQL, etc. Java (and probably other things as well) tries to determine the appropriate IP address to connect to by asking what the local hostname is, then doing an IP address lookup on that name. If that name isn't in the hosts table, then it'll try a DNS server. If the DNS server is slow, this can add a huge overhead. Likewise, if there are multiple DNS servers and one is timing out, it can add a huge overhead. IBM has run into this many times, so one of the first things they look for is to make sure your local host name is in the hosts file so this doesn't happen.

But, what Mark is doing doesn't use those network servers. He's running native C code that directly runs on the local system.

On 6/20/2017 9:30 AM, Diego Kesselman wrote:

Skott,

I've experienced slow response in QSHELL when hostname is a mess.

Mark,

Do you have any DNS configuration ? (CFGTCP -> Option 12) If so, are you using *LOCAL or *REMOTE ?

Do you have an entry on host tables for FQDN (hostname + domain name) and hostname ?

Regards

Diego Kesselman

El 20/06/17 a las 09:15, Scott Klement escribió:

Mark,

I must admit, I don't see what Diego's suggestion has to do with what you are doing... his suggestion is more related to Java programs being able to detect and connect to the local system -- which is known to perform slowly if you don't have the local host name in your hosts table. But, has nothing to do with your shell script.

But, I'm really shocked at the result... 15 seconds to run 'hostname'?! Seriously? This is just a simple program that retrieve's the system's hostname from memory and prints it. Shouldn't even take 1 second on a slow system.

Something is very wrong.

-SK

On 6/19/2017 9:53 PM, mlazarus wrote:

Diego,

hostname took about 15 seconds. java -version took about 50 seconds.

-mark