Thank you very much for your answers. > The hwlatdetect application detects system management interrupts > (SMIs). Such interrupts are installed by the BIOS and are used to manage > various things such as battery management, overheat protection and > emulation of legacy devices (e.g. IDE, PS/2 etc.). You may try to check > your BIOS settings and disable all these or similar features. In fact, after disabling almost all features in the bios, the problem is still here but a little bit reducted (there is just about 20ms latency now.. I think it's linked to the fact the thermal controller is disabled). But I didn't find any reference to SMIs in the bios, neither in the motherboard documentation (Supermicro X7DAL). The computer was not bought for doing realtime, so if it isn't working I think I'll change the computer to use one which has good latency during the tests. > One way to find out whether the spikes in the latency are due to > SMI(System Management Interrupt) is to read the MSR register that > keeps the count of SMIs. So, read the MSR in the start of the test > program and the end of the test and see whether the count has > increased. Unfortunately, it is model-specific-register and I am not > sure whether AMD supports it. I don't think all Intel processors > support it either. I know that Nehalem based Intel Core-i7 arrandale > processor supports counting SMI thru MSR 0x34 and I have not found it > documented in any Intel documentation but found in some reference BIOS > source. I have tested it with legacy USB interrupts and found it to > work. RDMSR is a privilege-0 instruction though. 0x34 is not working for me, it's not returning anything (just that he can't read) > root@station9:/home/xaf/RT# rdmsr 0x34 > rdmsr: CPU 0 cannot read MSR 0x00000034 The CPU I use here are two Intel(R) Xeon(R) CPU E5405 @ 2.00GHz, and I am unable to find any documentation about the results of MSR to know what argument I must use to see the number of SMIs. I'll investigate more on this... Thanks one more time ! -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
