Each I/O has to traverse several layers from application to
hardware. The block layer allows applications to access
diverse storage devices in a uniform way and provides the
storage device drivers with a single point of entry from all
applications, thus alleviating the complexity and diversity of
storage devices. In addition, the block layer mainly imple-
ments I/O scheduling, which performs operations called
merging and sorting to significantly improve the perfor-
mance of system as a whole.
The SCSI layer mainly constructs SCSI commands with
I/O requests from the block layer. The Libfc (FCP) layer
maps SCSI commands to Fibre Channel (FC) frames as
defined in standard Fibre Channel Protocol for SCSI
(FCP) [18]. The FCoE layer encapsulates FC frames into
FCoE frames or de-encapsulates FCoE frames into FC
frames as FC-BB-6 standard [3]. In other words, the SCSI,
FCP and FCoE layer mainly translate the I/O requests from
BLOCK layer to FCoE command frames. The Ethernet
driver transmits/receives FCoE frames to/from hardware.
The main I/O performance factors in Open-FCoE stack can
summarized as follows: (1) I/O-issuing Side translates the
I/O requests into FCoE format frames; (2) I/O Completion
Side informs the I/O-issuing threads of the I/O comple-
tions; (3) Parallel Process and Synchronization implements
parallel access on multi-core servers. In this section, we
describe and investigate the current Open-FCoE stack
according to the above mentioned factors.
2.1 Issue 1: High Synchronization Overhead from
Single Queu e & Shared Lock Mecha nism
Fig. 2 shows the I/O requests transmission process in the
SCSI/FCP/FCoE layers of Open-FCoE stack when multiple
cores/threads submit I/O requests to the remote target in
multi-core systems. We describe it as follows :
1) The SCSI layer builds the SCSI command structure
describing the I/O operation from the block layer;
then acquires the shared lock when: (1) enqueueing
the SCSI command into the shared queue in the SCSI
layer; and (2) dispatching the SCSI command from
the shared queue in the SCSI layer to the FCP layer.
2) The FCP layer builds the internal data structure (FCP
request) to describe the SCSI command from the
SCSI layer and acquires the shared lock when
enqueueing the FCP request into the internal shared
queue in the FCP layer. Then, it initializes an FC
frame with sk_buff structure for the FCP request, and
delivers the sk_buff structure to the FCoE layer.
3) The FCoE layer encapsulates FC frame into FCoE
frame, and then acquires the shared lock when:
(1) enqueueing the FCoE frame; and (2) dequeueing
the FCoE frame to transmit the frame to network
with the standard interface dev_queue_xmit().
Obviously, the shared lock provides the synchronization
operations on the shared queue in multi-core servers. How-
ever, such single queue & shared lock mechanism in SCSI/
FCP/FCoE layer decreases the capacity of software scalabil-
ity in multi-core systems.
For the purpose of improving scalability, modern servers
employ cache coherent Non Uniform Memory Access (cc-
NUMA) in multi-core architecture, such as the one depicted
in Fig. 3 that corresponds to the servers in our work. In such
architecture, there are some representative features [11],
[19], [20], [21], [22], [23], [24] that cause significantly impacts
on the software performance, such as Migratory Sharing,
False Sharing and significant performance difference when
accessing local or remote memory. These features bring
challenges to the developers for developing multi-threaded
software in cc-NUMA multi-core systems [25].
Fig. 1. Architecture of Linux Open-FCoE stack.
Fig. 2. Process of I/O requests transmission in the current Open-FCoE
stack.
Fig. 3. Multi-core architecture with cache coherent non-uniform memory
access (cc-NUMA).
2516 IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, VOL. 28, NO. 9, SEPTEMBER 2017
剩余12页未读，继续阅读
皮卡丘穿皮裤
- 粉丝: 187
- 资源: 955
我的内容管理
展开
最新资源
- 李兴华Java基础教程：从入门到精通
- U盘与硬盘启动安装教程：从菜鸟到专家
- C++面试宝典：动态内存管理与继承解析
- C++ STL源码深度解析：专家级剖析与关键技术
- C/C++调用DOS命令实战指南
- 神经网络补偿的多传感器航迹融合技术
- GIS中的大地坐标系与椭球体解析
- 海思Hi3515 H.264编解码处理器用户手册
- Oracle基础练习题与解答
- 谷歌地球3D建筑筛选新流程详解
- CFO与CIO携手：数据管理与企业增值的战略
- Eclipse IDE基础教程：从入门到精通
- Shell脚本专家宝典：全面学习与资源指南
- Tomcat安装指南：附带JDK配置步骤
- NA3003A电子水准仪数据格式解析与转换研究
- 自动化专业英语词汇精华：必备术语集锦
资源上传下载、课程学习等过程中有任何疑问或建议，欢迎提出宝贵意见哦~我们会及时处理！
点击此处反馈
