48 research outputs found
Evaluating TLB (Translation Lookaside Buffer) Performance Overhead for NVM (non-volatile Memory) Hybrid System
As the non-volatile memory (NVM) technology offers near-DRAM performance and near-disk capacity, NVM has emerged as a new storage class. Conventional file systems, designed for hard disk drives or solid-state drives, need to be re-examined or even re-designed for NVM storage. For example, new file systems such as NOVA, HMFS, HMVFS and Ext4-DAX, have been developed and implemented to fully leverage NVM’s characteristics, such as fast fine-grained access. This thesis research uses a variety of I/O workloads to evaluate the performance overhead of the TLB (translation lookaside buffer) in various file systems on emulated NVM storage systems, in which NVM resides on the memory bus. As NVM’s capacity becomes much greater than DRAM and applications’ footprints continue to increase rapidly, the number of TLB entries scales up with the same pace, leading to a significant amount of TLB misses. The goal of this research is to gain insights into file system optimizations on storage-class memory. Experimental results show that NVM based file systems can have 50% more TLB overhead compare to with conventional file systems, under the same file operations. Profiling based on performance counters show that TLB-friendly journaling/logging should be taken into consideration into future file system design
Improving the Performance and Endurance of Persistent Memory with Loose-Ordering Consistency
Persistent memory provides high-performance data persistence at main memory.
Memory writes need to be performed in strict order to satisfy storage
consistency requirements and enable correct recovery from system crashes.
Unfortunately, adhering to such a strict order significantly degrades system
performance and persistent memory endurance. This paper introduces a new
mechanism, Loose-Ordering Consistency (LOC), that satisfies the ordering
requirements at significantly lower performance and endurance loss. LOC
consists of two key techniques. First, Eager Commit eliminates the need to
perform a persistent commit record write within a transaction. We do so by
ensuring that we can determine the status of all committed transactions during
recovery by storing necessary metadata information statically with blocks of
data written to memory. Second, Speculative Persistence relaxes the write
ordering between transactions by allowing writes to be speculatively written to
persistent memory. A speculative write is made visible to software only after
its associated transaction commits. To enable this, our mechanism supports the
tracking of committed transaction ID and multi-versioning in the CPU cache. Our
evaluations show that LOC reduces the average performance overhead of memory
persistence from 66.9% to 34.9% and the memory write traffic overhead from
17.1% to 3.4% on a variety of workloads.Comment: This paper has been accepted by IEEE Transactions on Parallel and
Distributed System
Persistent Memory File Systems:A Survey
Persistent Memory (PM) is non-volatile byte-addressable memory that offers read and write latencies in the order of magnitude smaller than flash storage, such as SSDs. This survey discusses how file systems address the most prominent challenges in the implementation of file systems for Persistent Memory. First, we discuss how the properties of Persistent Memory change file system design. Second, we discuss work that aims to optimize small file I/O and the associated meta-data resolution. Third, we address how existing Persistent Memory file systems achieve (meta) data persistence and consistency
ECHOFS: a scheduler-guided temporary filesystem to leverage node-local NVMS
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The growth in data-intensive scientific applications poses strong demands on the HPC storage subsystem, as data needs to be copied from compute nodes to I/O nodes and vice versa for jobs to run. The emerging trend of adding denser, NVM-based burst buffers to compute nodes, however, offers the possibility of using these resources to build temporary file systems with specific I/O optimizations for a batch job. In this work, we present echofs, a temporary filesystem that coordinates with the job scheduler to preload a job's input files into node-local burst buffers. We present the results measured with NVM emulation, and different FS backends with DAX/FUSE on a local node, to show the benefits of our proposal and such coordination.This work was partially supported by the Spanish Ministry of Science and Innovation
under the TIN2015–65316 grant, the Generalitat de Catalunya under contract 2014–
SGR–1051, as well as the European Union’s Horizon 2020 Research and Innovation
Programme, under Grant Agreement no. 671951 (NEXTGenIO). Source code available
at https://github.com/bsc-ssrg/echofs.Peer ReviewedPostprint (author's final draft
Redesigning Transaction Processing Systems for Non-Volatile Memory
Department of Computer Science and EngineeringTransaction Processing Systems are widely used because they make the user be able to manage
their data more efficiently. However, they suffer performance bottleneck due to the redundant
I/O for guaranteeing data consistency. In addition to the redundant I/O, slow storage device
makes the performance more degraded. Leveraging non-volatile memory is one of the promising
solutions the performance bottleneck in Transaction Processing Systems. However, since the
I/O granularity of legacy storage devices and non-volatile memory is not equal, traditional
Transaction Processing System cannot fully exploit the performance of persistent memory.
The goal of this dissertation is to fully exploit non-volatile memory for improving the performance
of Transaction Processing Systems.
Write amplification between Transaction Processing System is pointed out as a performance
bottleneck. As first approach, we redesigned Transaction Processing Systems to minimize the
redundant I/O between the Transaction Processing Systems. We present LS-MVBT that integrates
recovery information into the main database file to remove temporary files for recovery.
The LS-MVBT also employs five optimizations to reduce the write traffics in single fsync() calls.
We also exploit the persistent memory to reduce the performance bottleneck from slow storage
devices. However, since the traditional recovery method is for slow storage devices, we develop
byte-addressable differential logging, user-level heap manager, and transaction-aware persistence
to fully exploit the persistent memory. To minimize the redundant I/O for guarantee data consistency,
we present the failure-atomic slotted paging with persistent buffer cache.
Redesigning indexing structure is the second approach to exploit the non-volatile memory
fully. Since the B+-tree is originally designed for block granularity, It generates excessive I/O
traffics in persistent memory. To mitigate this traffic, we develop cache line friendly B+-tree
which aligns its node size to cache line size. It can minimize the write traffic. Moreover, with
hardware transactional memory, it can update its single node atomically without any additional
redundant I/O for guaranteeing data consistency. It can also adapt Failure-Atomic Shift and
Failure-Atomic In-place Rebalancing to eliminate unnecessary I/O.
Furthermore, We improved the persistent memory manager that exploit traditional memory
heap structure with free-list instead of segregated lists for small memory allocations to minimize
the memory allocation overhead.
Our performance evaluation shows that our improved version that consider I/O granularity
of non-volatile memory can efficiently reduce the redundant I/O traffic and improve the
performance by large of a margin.ope