Preemptive Thread Block Scheduling with Online Structural Runtime Prediction for Concurrent GPGPU Kernels

Recent NVIDIA Graphics Processing Units (GPUs) can execute multiple kernels concurrently. On these GPUs, the thread block scheduler (TBS) uses the FIFO policy to schedule their thread blocks. We show that FIFO leaves performance to chance, resulting in significant loss of performance and fairness. To improve performance and fairness, we propose use of the preemptive Shortest Remaining Time First (SRTF) policy instead. Although SRTF requires an estimate of runtime of GPU kernels, we show that such an estimate of the runtime can be easily obtained using online profiling and exploiting a simple observation on GPU kernels' grid structure. Specifically, we propose a novel Structural Runtime Predictor. Using a simple Staircase model of GPU kernel execution, we show that the runtime of a kernel can be predicted by profiling only the first few thread blocks. We evaluate an online predictor based on this model on benchmarks from ERCBench, and find that it can estimate the actual runtime reasonably well after the execution of only a single thread block. Next, we design a thread block scheduler that is both concurrent kernel-aware and uses this predictor. We implement the SRTF policy and evaluate it on two-program workloads from ERCBench. SRTF improves STP by 1.18x and ANTT by 2.25x over FIFO. When compared to MPMax, a state-of-the-art resource allocation policy for concurrent kernels, SRTF improves STP by 1.16x and ANTT by 1.3x. To improve fairness, we also propose SRTF/Adaptive which controls resource usage of concurrently executing kernels to maximize fairness. SRTF/Adaptive improves STP by 1.12x, ANTT by 2.23x and Fairness by 2.95x compared to FIFO. Overall, our implementation of SRTF achieves system throughput to within 12.64% of Shortest Job First (SJF, an oracle optimal scheduling policy), bridging 49% of the gap between FIFO and SJF.Comment: 14 pages, full pre-review version of PACT 2014 poste

Notes on Euclidean de Sitter space

We discuss issues relating to the topology of Euclidean de Sitter space. We show that in (2+1) dimensions, the Euclidean continuation of the`causal diamond', i.e the region of spacetime accessible to a timelike observer, is a three-hemisphere. However, when de Sitter entropy is computed in a `stretched horizon' picture, then we argue that the correct Euclidean topology is a solid torus. The solid torus shrinks and degenerates into a three-hemisphere as one goes from the `stretched horizon' to the horizon, giving the Euclidean continuation of the causal diamond. We finally comment on the generalisation of these results to higher dimensions.Comment: 10 pages, 2 figures, LaTeX, reference adde

Structure Space of Model Proteins --A Principle Component Analysis

We study the space of all compact structures on a two-dimensional square lattice of size $N=6\times6$. Each structure is mapped onto a vector in $N$-dimensions according to a hydrophobic model. Previous work has shown that the designabilities of structures are closely related to the distribution of the structure vectors in the $N$-dimensional space, with highly designable structures predominantly found in low density regions. We use principal component analysis to probe and characterize the distribution of structure vectors, and find a non-uniform density with a single peak. Interestingly, the principal axes of this peak are almost aligned with Fourier eigenvectors, and the corresponding Fourier eigenvalues go to zero continuously at the wave-number for alternating patterns ($q=\pi$). These observations provide a stepping stone for an analytic description of the distribution of structural points, and open the possibility of estimating designabilities of realistic structures by simply Fourier transforming the hydrophobicities of the corresponding sequences.Comment: 14 pages, 12 figures, Conclusion has been modifie

An Efficient Explicit Error Notification with Adaptive Packet Size Mechanism to Improve TCP Performance in LEO Network

LEO satellite network plays a major role in the design of next generation internet. Due to high error rate of satellite link and absence of error handling mechanism in TCP, the end-to-end performance of existing TCP based applications over the satellite environment degrades substantially. Many research contributions have shown that with the help of explicit loss notification, sender is able to discriminate between loss due to congestion and loss due packet corruption, thereby avoids the unnecessary reduction of sending rate. Few studies, however, have mentioned that sending smaller size packets or optimum size packets can increase the success of packet delivery. The contribution of this work is to propose an integrated solution to improve the end-to-end performance of TCP using backward explicit notification of GSL (Ground-to-Satellite link) errors and optimum packet size calculation at TCP sender. With help of simulation experiments, we show that proposed scheme improves the end-to-end performance of TCP based applications over high error rate satellite links

Knot Solitons

The existence of ring-like and knotted solitons in O(3) non-linear sigma model is analysed. The role of isotopy of knots/links in classifying such solitons is pointed out. Appearance of torus knot solitons is seen.Comment: Latex 9 pages + 2 eps figure

A Study of Mobile User Movements Prediction Methods

For a decade and more, the Number of smart phone users count increasing day by day. With the drastic improvements in Communication technologies, the prediction of future movements of mobile users needs also have important role. Various sectors can gain from this prediction. Communication management, City Development planning, and locationbased services are some of the fields that can be made more valuable with movement prediction. In this paper, we propose a study of several Location Prediction Techniques in the following area

Decreasing the Polymerization Potential Improves the Selectivity of PPD-Coated Disc Biosensors for Glutamate

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The selectivity of glutamate microdisc biosensors coated with poly(o-phenylenediamine) (PPD) as the interference-rejecting layer against ascorbic acid was observed to be very low. Enhancement in the selectivity was noticed when the electropolymerization potential for the polymerization of the o-phenylenediamine monomer was decreased from 0.65 V to 0.40 V vs. Ag/AgCl. The selectivity coefficient increased from −34.93±3.75% (n = 5) to 53.05 ± 4.33% (n = 3). Decreasing the polymerization potential decreases the rate of formation of the polymer and improves the compactness of the polymer layer formed, thereby increasing the selectivity of the electrodes

Genus Zero Correlation Functions in c<1 String Theory

We compute N-point correlation functions of pure vertex operator states(DK states) for minimal models coupled to gravity. We obtain agreement with the matrix model results on analytically continuing in the numbers of cosmological constant operators and matter screening operators. We illustrate this for the cases of the $(2k-1,2)$ and $(p+1,p)$ models.Comment: 11 pages, LaTeX, IMSc--92/35. (revised) minor changes plus one reference adde