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TOPIC: High CPU result in slow ping response time???

High CPU result in slow ping response time??? 6 years 11 months ago #33161

  • Kanasai
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Question: Would high CPU on the remote server will result in degraded ping response time??
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Re: High CPU result in slow ping response time??? 6 years 11 months ago #33165

  • FlipRich
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I dont think so. Ping replies take up an insignificant amount of CPU resource. Network congestion or faulty interfaces will result in slow ping echos.
Rich
Network Engineer /CCNP, CCNA-S
Tallahassee, FL
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Re: High CPU result in slow ping response time??? 6 years 11 months ago #33166

  • TheBishop
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I'm sort-of with FlipRich on this one, except to wonder why your CPU is so high. If it's a user-mode program that's simply hogging it then no, I wouln't expect higher ping times. But if the high CPU is simply a symptom of a box that is running short of resources generally or being hammered then along with high CPU you might see low available memory and high disk activity. Those will slow the OS down and that could well degrade the ping responses
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Re: High CPU result in slow ping response time??? 6 years 11 months ago #33177

  • S0lo
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Ok, this sounded interesting so I've done a tiny experiment here.

First I ran a CPU intensive simulation that takes like 98% of CPU time. Then on another PC tried to ping it like this:

ping 192.168.1.10 -l 65500

192.168.1.10 is obviously the target and "-l 65500" will make giant ping packets of this size. Result is, NO miss, All pings where replied. I also tried normal ping without "l 65500" too, still the same, all replied.

Then I tried to make the simulation program run with higher priority, I tried all "Above Normal", "High" and "Real Time". All replied again!!

Third trial, I opened 20 pinging console windows (using some crazy DoS program ;)). No hope again!!!!. Now I really wanted to kill, so I tried 200 pinging console windows...... and at last a "Request timed out." on many many pings :twisted:

It's worth saying here that running those 200 continuous pings even without the CPU intensive program on the target DID cause allot of reply loss. Surprisingly, the 200 pings only raised the CPU usage of the target to like 30%-35%, and there were jumps up and down!!. This probably indicates that the bottle neck was anything but not CPU. Notice that this target PC is really an old horse with only 450Mhz CPU.

By further monitoring on the target, it seams that the subsystem that replies to pings are related to INTERRUPTS, DPC (Deferred Procedural Calls) and looks like they are running on a much higher priority.

So yes, I agree with the above folks :)
Studying CCNP...

Ammar Muqaddas
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www.firewall.cx
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Re: High CPU result in slow ping response time??? 6 years 11 months ago #33179

  • jester
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it happens when the target machine is running a firewall having a conditions for ICMP , which may increase the CPU usage rate ,other than that the network may be filled with Broadcast packets or as flip said may be due to congestion in the network may cause slow ping response.
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