On Thu, Jun 14, 2012 at 6:04 PM, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote: > On Tue, 2012-06-12 at 20:57 +0800, Luming Yu wrote: >> The Goal is to test out hardware/BIOS caused >> problems in 2 minutes. To me, capable of measuring the intrinsic of >> hardware on which we build our software is always a better idea than >> blindly looking for data from any documents. In current version of the >> tool, we have a basic sampling facility and TSC test ready for x86. I >> plan to add more test into this tool to enrich our tool set in Linux. >> >> > There's SMI damage around on much longer periods than 2 minutes. Right, it's a problem that if we run the tool when SMI is not triggered. My rough idea is to come up with some ideas to scan the system. Not entirely sure but 2 minutes could be sufficient to finish such scan on a normal laptop. The question is how we scan? We may need to adjust the 2 minutes goal accordingly based on the method of scan and the size of machine to scan. > > Also, you can't really do stop_machine for 2 minutes and expect the > system to survive. By design, the test thread suppose to, by default, for tsc measurement, spend sample_width/sample_window of cpu cycles in stop_machine context on sampling. The left cpu cycles yields to other threads in msleep_interruptible. The default sample_width is 500us, the default sample_window is 1ms. > > Furthermore, I think esp. on more recent chips there's better ways of > doing it. Right , the reference to PMU counts will make the tool more useful. > > For Intel there's a IA32_DEBUGCTL.FREEZE_WHILE_SMM_EN [bit 14], if you > program a PMU event that ticks at the same rate as the TSC and enable > the FREEZE_WHILE_SMM stuff, any drift observed between that and the TSC > is time lost to SMM. It also has MSR_SMI_COUNT [MSR 34H] which counts > the number of SMIs. > > For AMD there's only event 02Bh, which is SMIs Received. I'm not sure it > has anything like the FREEZE or if the event is modifyable to count the > cycles in SMI. It's in to-do-list for version 0.2 of the tool. Thanks!!! -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
