Steven Rostedt wrote: > On Fri, 10 Jul 2009, Darren Hart wrote: > > >> Subrata Modak wrote: >> >>> On Fri, 2009-07-10 at 22:00 +0530, Sripathi Kodi wrote: >>> >>>> On Wednesday 08 July 2009 23:43:53 Subrata Modak wrote: >>>> >>>>> Darren/Sri/Gowri, >>>>> >>>>> Where do you want me to put this exactly inside the RT tree ? >>>>> >>>> Hi Subrata, >>>> >>>> Going by how the tests are organized currently, I think this should go >>>> into it's own directory under testcases/realtime/func. We will need to >>>> add a makefile to it. Are you looking at us to help you with this? >>>> >>> Correct. Please send me a patch which integrates it into RT tests build, >>> install & run. >>> >> Just got back from a week vacation and am burning through mail as fast as I >> can :-) Haven't had a look yet, but does this test use librttest.h? I >> suspect >> not. We'll need to adapt it to run within the existing ltp real-time testing >> framework, which includes things like buffered output as well as mlocking >> support. >> >> Lastly, I'm not sure this test does anything effectively different than >> prio-wake, already in the tree.
Just to add to Steven's comments below: At the time that rt-migrate was written, LTP and others lacked sufficient resolution in their testing to reliably find the type of problem that rt-migratate can pinpoint quickly. IIRC, "football" was potentially capable of finding these types of scheduler bugs, but it often failed to find it at all, or it took 24h+ of runtime to find it. Steven's test could find it in under a second or two. And, as Steven mentions below, rt-migrate is additionally designed to look at the top N prio tasks (where N = cpu-count) That said, I am not familiar with "prio-wake" so I am not sure if its new or if it has direct overlap with Steven's test or not. >> My other concerns with the test are its >> explicit 1ms preemption criteria (as Steven described it anyway). We are >> trying to move away from criteria being inherent in measurement tests, and 1 >> ms seems like an awfully long priority inversion to be an acceptable criteria >> to many users. >> >> Steven, am I missing something conceptually here? >> > > Hmm, I missed this email, sorry for the late reply. > > What does prio-wake do? > > This test is what I used to develop the rt scheduler in mainline (as well > as in -rt). It wakes up N+1 tasks with lowering real time priorities. > Where N is the number of CPUs in the system. Then it makes sure that the > these tasks spread out across the CPUs. Most tests just test the highest > priority task in the system. But those tests usually miss the second > highest prio task in the system. If you have a second highest prio task in > the system and a CPU is available to run, then it should run on that CPU. > But what happens is that it can wait to be migrated and can take millisecs > to wake up. > > This test makes sure that all the high prio tasks that are in the running > state are actually running on a CPU if it can. > > Make sense? > > (BTW, current -rt and mainline now fail this test :-? ) > > -- Steve > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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