Is latency an issue when using a Mesa card?
- spangledboy
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29 Jun 2012 19:22 #21462
by spangledboy
Replied by spangledboy on topic Re:Is latency an issue when using a Mesa card?
Ok, i've just done a little bit of work - the PC that I decided to take was a little over-specced, but I decided to get the newest/best pc from the pile that I could find:
Dell Optiplex 755 Small form factor
8GB RAM (yes, I know we're running a 32bit OS here, but I may do something else with the PC in future)
2.4GHz Core 2 Duo Processor (both cores enabled)
ATI Radeon X300SE PCI-X graphics card
When I ran the latency test with the default configuration I had jitter of about 49,000ns for the 1ms thread and 35,000ns for the 25us thread.
I applied the isolcpus changes as described here: wiki.linuxcnc.org/cgi-bin/wiki.pl?The_Is..._Parameter_And_GRUB2 and the jitter is now 42,700 for the 1ms thread and 16,200 for the 25us thread.
Definitely an improvement! I can see the difference in the CPU graphs on System Monitor - one CPU is doing all the work for the other stuff I have running and the other is hardly doing anything (presumably only the Latency Test). More importantly, the jitter hasn't changed since I started running the test, whereas before it would start low, then jump up to the max figure as time went by.
I'll leave the test running to see if I have any spikes due to SMI and update this thread later.
Ben
Dell Optiplex 755 Small form factor
8GB RAM (yes, I know we're running a 32bit OS here, but I may do something else with the PC in future)
2.4GHz Core 2 Duo Processor (both cores enabled)
ATI Radeon X300SE PCI-X graphics card
When I ran the latency test with the default configuration I had jitter of about 49,000ns for the 1ms thread and 35,000ns for the 25us thread.
I applied the isolcpus changes as described here: wiki.linuxcnc.org/cgi-bin/wiki.pl?The_Is..._Parameter_And_GRUB2 and the jitter is now 42,700 for the 1ms thread and 16,200 for the 25us thread.
Definitely an improvement! I can see the difference in the CPU graphs on System Monitor - one CPU is doing all the work for the other stuff I have running and the other is hardly doing anything (presumably only the Latency Test). More importantly, the jitter hasn't changed since I started running the test, whereas before it would start low, then jump up to the max figure as time went by.
I'll leave the test running to see if I have any spikes due to SMI and update this thread later.
Ben
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