The new-ish Fermi class of NVidia GPUs has much better hardware support for multitasking than its predecessors. I don't know of any project that is using this officially so far, perhaps because Fermi-class GPUs are still expensive and comparatively rare. but prices are falling and sales increasing - they will become widespread eventually.
Given the extensive use of third-party applications at SETI, it is inevitable that experimentation has taken place. Empirically, several commentators have found the same answer: the SETI Fermi application (as supplied by NVidia itself) runs most productively when three instances are scheduled to run concurrently. But with the current FIFO scheduling and no pre-emption, this leads to problems when running, as BOINC is designed to do, multiple projects. Consider http://a.imageshack.us/img441/9485/notaskswitchwithcuda.png The three SETI tasks finish asychronously. Each time one exits, 0.34 GPUs become available: but that's not enough to launch the GPUGrid tasks ahead of them in the FIFO queue. So BOINC deals yet another SETI (or SETI Beta, which I've set up similarly) task from the bottom of the pack. Presumably, this would continue indefinitely, until either fractional GPU tasks from all other projects ran dry, or imminent deadline pressure forced GPUGrid into 'High Priority'. This is analogous to the situation we saw with AQUA and multi-threaded CPU applications, where the MT app had a tendency to hog the CPU and keep out other projects. That's been sorted now: this one hasn't. I'm sure the BOINC client will complete the work before deadline (although I've intervened manually, and these tasks won't get a chance to hang around that long). But that isn't the point. The science behind GPUGrid requires that tasks be returned in a timely fashion. Earlier results are required to generate the starting conditions for later jobs. Any scientific results of value will depend on a long chain of job - process - result - new job - process - result - new job..., and so on. Although they allow a deadline of up to five days, to allow slower and part-time GPUs to participate, they prefer results back within 24 hours if possible. FIFO scheduling without allowance for fractional usage is preventing this. The basic plumbing for task-switch GPU scheduling was in place as far back as last December, with the introduction of cuda_short_term_debt and ati_short_term_debt (see for example changeset 19898). Is there any chance of returning to this functional area of BOINC development, before the next quantum leap in technology overtakes us? _______________________________________________ boinc_dev mailing list [email protected] http://lists.ssl.berkeley.edu/mailman/listinfo/boinc_dev To unsubscribe, visit the above URL and (near bottom of page) enter your email address.
