Hi: * Juerg Haefliger <juergh at gmail.com> [2007-07-25 22:39:40 -0700]: > > >> 1.53 seconds to read "0\n" ! :) > > >> > > >> Any idea if this is a hardware or software delay? I haven't yet dug > > >> into profiling the kernel code to see what might be taking so long... > > > > > > It's simple: We have to read a lot of registers which we can only get > > > to via I2C which is veeerrrrryyyyy sloooooowwwwww. Max rate for standard I2C/SMBus is 100KHz. However, the hardware which is most common on PCs usually runs at something like 10KHz. > > Ok, I thought it might be along those lines. Is there any other > > performance impact to the system while it's waiting for the I2C bus? > > Good question, I don't know. That's more a question for the I2C > mailing list. Jean? It depends on the specific I2C bus driver. All of the most common ones use polling, so unfortunately you will see CPU % go to 100 during that 1.5 sec. Regards, -- Mark M. Hoffman mhoffman at lightlink.com
