On Tue, Mar 31, 2015 at 08:32:16AM -0700, Dave Johansen wrote: > I am not familiar with the low level details of disk I/O but I'm sure that > they are far more complicated than my basic assumptions, but my concern is > how can a disk-bound process steal cycles from a CPU-bound one that is not > access the disk at all. The lwn.net articles that drago01 linked to helped > shed some light on what's going on, but it sounds like there is still some > potential work that could be done to help improve the situation. When you run the cpu load test program, where do you write the statistics to? For a fair test you probably want to change the program so it stores them in preallocated memory and prints them at the end of the test. Almost anything else -- even writing to a file in /dev/shm -- could block waiting on other slow requests. And if you're writing them to stdout under X11, then you'd have to be sure that nothing else in your terminal / X stack could ever swap or issue any kind of I/O, which is probably impossible. Perhaps writing to a Linux virtual console might be safe. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
