Evaluating SMI (System Management Interrupt) latency on Linux-CentOS/Intel machine

Question

I am interested in evaluating the behavior (latency, frequency) of SMI handling on Linux machine running CentOS and used for a (very) soft real time application.

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Answer 1

SMI will put your system into SMM (System Management Mode) mode, which will postpone the normal execution of kernel during the SMI handling time period. In other words, SMM is neither real mode nor protected mode as we know of normal operation of kernel, instead it executes some special instruction kept in SMRAM (stored in Bios Firmware). To detect it's latency you can try to trigger an SMI (it can be software generated) and try to catch the total time spent in SMM mode. To accomplish this you can write a Linux kernel module, cause you'll be require some special privileges to issue an SMI (I think).

For real time systems I think it's nice if you can avoid these sort of interrupts like SMI.