14 research outputs found

    Unblinding the OS to Optimize User-Perceived Flash SSD Latency

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    In this paper, we present a flash solid-state drive (SSD) optimization that provides hints of SSD internal behaviors, such as device I/O time and buffer activities, to the OS in order to mitigate the impact of I/O completion scheduling delays. The hints enable the OS to make reliable latency predictions of each I/O request so that the OS can make accurate scheduling decisions when to yield or block (busy wait) the CPU, ultimately improving user-perceived I/O performance. This was achieved by implementing latency predictors supported with an SSD I/O behavior tracker within the SSD that tracks I/O behavior at the level of internal resources, such as DRAM buffers or NAND chips. Evaluations with an SSD prototype based on a Xilinx Zynq-7000 FPGA and MLC flash chips showed that our optimizations enabled the OS to mask the scheduling delays without severely impacting system parallelism compared to prior I/O completion methods.We would like to thank the anonymous USENIX HotStorage reviewers. This research was supported by NextGeneration Information Computing Development Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Plannig (2015M 3C 4A7065646).OAIID:RECH_ACHV_DSTSH_NO:A201608543RECH_ACHV_FG:RR00200003ADJUST_YN:EMP_ID:A002712CITE_RATE:DEPT_NM:컴퓨터공학부EMAIL:[email protected]_YN:CONFIRM:

    Studies in Exascale Computer Architecture: Interconnect, Resiliency, and Checkpointing

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    Today’s supercomputers are built from the state-of-the-art components to extract as much performance as possible to solve the most computationally intensive problems in the world. Building the next generation of exascale supercomputers, however, would require re-architecting many of these components to extract over 50x more performance than the current fastest supercomputer in the United States. To contribute towards this goal, two aspects of the compute node architecture were examined in this thesis: the on-chip interconnect topology and the memory and storage checkpointing platforms. As a first step, a skeleton exascale system was modeled to meet 1 exaflop of performance along with 100 petabytes of main memory. The model revealed that large kilo-core processors would be necessary to meet the exaflop performance goal; existing topologies, however, would not scale to those levels. To address this new challenge, we investigated and proposed asymmetric high-radix topologies that decoupled local and global communications and used different radix routers for switching network traffic at each level. The proposed topologies scaled more readily to higher numbers of cores with better latency and energy consumption than before. The vast number of components that the model revealed would be needed in these exascale systems cautioned towards better fault tolerance mechanisms. To address this challenge, we showed that local checkpoints within the compute node can be saved to a hybrid DRAM and SSD platform in order to write them faster without wearing out the SSD or consuming a lot of energy. A hybrid checkpointing platform allowed more frequent checkpoints to be made without sacrificing performance. Subsequently, we proposed switching to a DIMM-based SSD in order to perform fine-grained I/O operations that would be integral in interleaving checkpointing and computation while still providing persistence guarantees. Two more techniques that consolidate and overlap checkpointing were designed to better hide the checkpointing latency to the SSD.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137096/1/sabeyrat_1.pd

    Unblinding the OS to Optimize User-Perceived Flash SSD Latency

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    Abstract In this paper, we present a flash solid-state drive (SSD) optimization that provides hints of SSD internal behaviors, such as device I/O time and buffer activities, to the OS in order to mitigate the impact of I/O completion scheduling delays. The hints enable the OS to make reliable latency predictions of each I/O request so that the OS can make accurate scheduling decisions when to yield or block (busy wait) the CPU, ultimately improving user-perceived I/O performance. This was achieved by implementing latency predictors supported with an SSD I/O behavior tracker within the SSD that tracks I/O behavior at the level of internal resources, such as DRAM buffers or NAND chips. Evaluations with an SSD prototype based on a Xilinx Zynq-7000 FPGA and MLC flash chips showed that our optimizations enabled the OS to mask the scheduling delays without severely impacting system parallelism compared to prior I/O completion methods

    Diagnostic Significance of Exosomal miRNAs in the Plasma of Breast Cancer Patients

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    Poster Session AbstractsBackground and Aims: Emerging evidence that microRNAs (miRNAs) play an important role in cancer development has opened up new opportunities for cancer diagnosis. Recent studies demonstrated that released exosomes which contain a subset of both cellular mRNA and miRNA could be a useful source of biomarkers for cancer detection. Here, we aim to develop a novel biomarker for breast cancer diagnosis using exosomal miRNAs in plasma. Methods: We have developed a rapid and novel isolation protocol to enrich tumor-associated exosomes from plasma samples by capturing tumor specific surface markers containing exosomes. After enrichment, we performed miRNA profiling on four sample sets; (1) Ep-CAM marker enriched plasma exosomes of breast cancer patients; (2) breast tumors of the same patients; (3) adjacent non-cancerous tissues of the same patients; (4) Ep-CAM marker enriched plasma exosomes of normal control subjects. Profiling is performed using PCR-based array with human microRNA panels that contain more than 700 miRNAs. Results: Our profiling data showed that 15 miRNAs are concordantly up-regulated and 13 miRNAs are concordantly down-regulated in both plasma exosomes and corresponding tumors. These account for 25% (up-regulation) and 15% (down-regulation) of all miRNAs detectable in plasma exosomes. Our findings demonstrate that miRNA profile in EpCAM-enriched plasma exosomes from breast cancer patients exhibit certain similar pattern to that in the corresponding tumors. Based on our profiling results, plasma signatures that differentiated breast cancer from control are generated and some of the well-known breast cancer related miRNAs such as miR-10b, miR-21, miR-155 and miR-145 are included in our panel list. The putative miRNA biomarkers are validated on plasma samples from an independent cohort from more than 100 cancer patients. Further validation of the selected markers is likely to offer an accurate, noninvasive and specific diagnostic assay for breast cancer. Conclusions: These results suggest that exosomal miRNAs in plasma may be a novel biomarker for breast cancer diagnosis.link_to_OA_fulltex
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