CLAM: Compiler Lease of Cache Memory

Caching is a common solution to the data movement performance bottleneck of today’s computational systems and networks. Traditional caching examines program behavior and cache optimization separately, limiting performance. Recently, a new cache policy called Compiler Lease of cAche Memory (CLAM), has been suggested for program-based cache management. CLAM manages cache memory by allowing the compiler to assign leases, or lifespans, to cached items over a hardware-software interface, known as lease cache. Lease cache affords new performance potential, by way of program-driven cache optimization. It is applicable to existing cache architecture optimizations, and can be used to emulate other cache policies. This paper presents the first functional hardware implementation of lease cache for CLAM support. Lease cache hardware architecture is first presented, along with CLAM hardware support systems. The cache is emulated on an FPGA, and benchmarked using a collection of scientific kernels from the PolyBench/C suite, for three CLAM lease assignment policies: Compiler Assigned Reference Leasing (CARL), Phased Reference Leasing (PRL), and Fixed Uniform Leasing (FUL). CARL and PRL are able to achieve superior performance to Least Recently Used (LRU) replacement, while FUL is shown to serve as a safety mechanism for CLAM. Novel spectrum-based cache tenancy analysis verifies PRL’s effectiveness in limiting cache utilization, and can identify changes in the working-set that cause the policy to perform adversely. This suggests that CLAM is extendable to more complex workloads if working-set transitions can elicit a similar change in lease policy. Being able to do so could yield appreciable performance improvements for large and highly iterative workloads like tensors

LVAD Occlusion Condition Monitoring Using State Augmented Acoustic Spectral Images

Each year, thousands of people die from heart disease and related illnesses due to the lack of available donor organs. Left ventricular assist devices (LVADs) aim to mitigate that occurrence, serving as a bridge-to-surgery option. While short term survival rates of LVAD patients near that of orthotopic surgery they are not viable long term options due to varied reasons. This work examines one cause, outlet graft thrombosis, and develops an algorithm for increasingly robust classification of device condition as it pertains to thrombosis or more generally occlusion. In order to do so an in vitro heart simulator is developed so that varying degrees of signal non-stationarity can be simulated and tested over a wide range of physiological blood pressure and heart rate conditions. Using a seeded-fault methodology, acoustics are acquired at the LVAD outlet graft location and subsequent spectral images of the sounds are developed. Statistical parameters from the images are used as features for classification using a support vector machine (SVM) which yields promising results. Given a comprehensive training space classification can be performed to fair accuracies (roughly 80%) using only the spectral image parameters. However, when the training space is limited augmenting the image features with patient state parameters elicits more robust identification. The algorithm developed in this work offers non-invasive diagnostic potential for LVAD conditions otherwise requiring invasive means

Anticholinergic medications associated with falls and frailty in people with HIV

BackgroundAnticholinergic medications (ACMs) are associated with poorer age-related outcomes, including falls and frailty. We investigate associations between ACM use and recurrent falls and frailty among older (aged ≥50 years) people with HIV in the POPPY study.MethodsAnticholinergic potential of co-medications at study entry was coded using the anticholinergic burden score, anticholinergic risk score, and Scottish Intercollegiate Guidelines Network score; drugs scoring ≥1 on any scale were defined as ACM. Associations with recurrent falls (two or more falls in the previous 28 days) and frailty (modified Fried's) were assessed using logistic regression adjusting for (1) possible demographic/lifestyle confounders and (2) clinical factors and depressive symptoms (Patient Health Questionnaire-9).ResultsACM use was reported by 193 (28%) of 699 participants, with 64 (9%) receiving two or more ACM; commonly prescribed ACMs were codeine (12%), citalopram (12%), loperamide (9%), and amitriptyline (7%). Falls were reported in 63/673 (9%), and 126/609 (21%) met the frailty criteria. Both recurrent falls and frailty were more common in ACM users than in non-users (recurrent falls: 17% in users vs. 6% in non-users, p ConclusionsACM are commonly prescribed for people living with HIV, and evidence exists for an association with recurrent falls and frailty. Clinicians should be alert to this and reduce ACM exposure where possible.</p