Hi Steve, On Thu, Oct 18, 2007 at 09:38:44AM -0400, Steven Rostedt wrote: > > -- > When I'm asked what language is my mother tongue, > I simply answer "C". > > On Thu, 18 Oct 2007, Ankita Garg wrote: > > > > > Any thoughts on where in the code could these large latencies be > > > > attributed to? > > > > > > If the max latency is usually the first one, it's could be the page > > > fault the signal handler is taking the first time it is executed. > > > > Thanks for looking into this. Attaching the entire log from the testrun. > > It indicates that in each run of the 10000 iterations, there are about 100+ > > failures, with large iterations. Also, on intrumenting the testcode to > > find out the iterations which see large latencies, I see that as the > > number of iterations increase, the latencies increase. > > OK, this doesn't look like page faulting issues. But it is still a good > idea to add mlock to any RT tests. > > Could this possible be simply cache misses that cause this? There's a bit > of code to send a signal. What would the impact of cold cache be on this? > > One way is to see the mininum run of running with cached disabled. Not > sure if there's any way to disable cache via a kernel command line. Of > course that would make the system very slow to boot ;-) > The machines I am working on does not support disabling caches via BIOS and as Documentation/memory.txt suggests, BIOS seems to be the only way. Also, mlocking did not make any difference in the latencies. > -- Steve -- Regards, Ankita Garg (ankita@xxxxxxxxxx) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India - 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
