Hi, I uploaded a unfinished I/O testsuite for PVFS2 to http://www.rzuser.uni-heidelberg.de/~jkunkel2/direct-io-0.1-dist.tgz. This testsuite tries several I/O strategies.
There is still a lot to do, but I wanted to get some feedback from you guys, and maybe one of you can run the test on a RAID system ? The package consists of 2 source files, one uses either AIO or threads with direct I/O or without and the other one uses a extension contained in a modified libposix-aio directory. This extension uses the linux kernels I/O submit and io_getevents function to submit as many jobs as possible to the kernel. On the other hand io_getevents tries to wait for the completion of the current pending job number. This is the difference between my modifications and the aio default, without signals one must periodically check if one of the jobs is finished or use aio_suspend which blocks until at least one op of a given list is finished. Then the whole list has to be iterated to figure out which one finished. With the simple modifications this is not necessary, io_getevents returns only finished ops, thus the iteration is unncecessary. This is only experimental and I want to see the performance difference (if any) by feeding the kernel scheduler as good as possible. So, far I haven't seen difference to the threaded version, maybe I have to set the iteration to a higher value or try on a different system ? Right now I do not run the glibc / aio test, due to the fact that there shouldn't be a performance difference for a single file. However, it can be linked against libposix-aio, however this library is by default not thread safe... Also the package contains some (incomplete) results I got with one of our machines. You can simple build the graphs by running "make graphs". If you got some cool ideas in which direction the test should go, I would be happy, right now I hope more data will help to figure out which test might be appropriate. Thanks, julian _______________________________________________ Pvfs2-developers mailing list Pvfs2-developers@beowulf-underground.org http://www.beowulf-underground.org/mailman/listinfo/pvfs2-developers
