Nicholas Mc Guire wrote: > >> I'm writing to tell you about a project I'm working on. >> I'm trying to collect as much information as I can about >> testing real time performance of Linux. > >> I've started a wiki page at: >> http://tree.celinuxforum.org/CelfPubWiki/RealtimeTestingBestPractices >> (which is on CELF's wiki) > > The tests noted in the LKML post on this page are very problematic, ping > -f is not testing RT at all, it keeps the kernel in a very small active > page set thus reducing page related penalties, the while loop using dd > is also not too helpfull as it will de-facto run only in memory and cause > absolutely no disk/mass-storage related interaction (try the same with > mount -o remount,sync / first and it will be devastating ! (limited to > ext2/ext3/ufs)) > > The big problem with RT tests published is that they are all looking at > the good case, they are loading the system but assuming successfull > operations. The worst cases pup up when you run in the error paths of > the kernel - then a trivial application can induce very large jitter in > the system (run crashme in the background and rerun the tests...) > > Also lmbench can give a statistic view of things (and not even that very > precisely in some case i.e. context switch measurements are flawed) so > this is not of much help for descision makers which variant to use - it > does not help if the average performance is good but the mobile phone or > mp3 klicks at 1s intervales "deterministically" - so I guess RT > benchmarks need a notion of usage-profile to be of value. > > >> However, I think this material would be better placed >> on the Linux RT wiki at: http://rt.wiki.kernel.org/index.php/Main_Page >> Does anyone have any problem with me moving the content to there, >> and continuing my attempt to document this on that site? > > > Note that this page is dedicated to RT-preempt and will most likely not > cover the other variants of RT Linux availabe - so it might well be a > good idea to maintain an independant page but cross-link them ? > >> Note that there's some duplication of content with other >> pages on the RT wiki. I'll try to clean this up during the move. > >> Any comments or suggestions are welcome. > >> If you have done RT testing, and especially if you have published >> information I can look at (and link to), please contact me. > > There are a number of publications related to both benchmarking and > analysis of hardware related artefacts (cache,BTB,TLB,etc.) which were > published at the real-time Linux Workshops - should I collect them > together and send you those as tar.bz2 or just the links ? > I would definitely be interested in such material myself. We are actually using the RT patches in real world scenarios on probably 50+ systems (some are development workstations and others are hardware-in-the-loop simulation test systems) and they perform very well. However, it would be nice to have a battery of tests (both correctness and determinism)that could be used to compare future versions. > hofrat - 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 -- kr - 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
