Invention Grant
US09298375B2 Method and apparatus for returning reads in the presence of partial data unavailability 有权
在存在部分数据不可用的情况下返回读取的方法和装置

  • Patent Title: Method and apparatus for returning reads in the presence of partial data unavailability
  • Patent Title (中): 在存在部分数据不可用的情况下返回读取的方法和装置
  • Application No.: US13779112
    Application Date: 2013-02-27
  • Publication No.: US09298375B2
    Publication Date: 2016-03-29
  • Inventor: Erik Cota-RoblesThomas A. Phelan
  • Applicant: VMware, Inc.
  • Applicant Address: US CA Palo Alto
  • Assignee: VMware, Inc.
  • Current Assignee: VMware, Inc.
  • Current Assignee Address: US CA Palo Alto
  • Main IPC: G06F3/06
  • IPC: G06F3/06 G06F9/30
Method and apparatus for returning reads in the presence of partial data unavailability
Abstract:
Techniques are disclosed for reducing perceived read latency. Upon receiving a read request with a scatter-gather array from a guest operating system running on a virtual machine (VM), an early read return virtualization (ERRV) component of a virtual machine monitor fills the scatter-gather array with data from a cache and data retrieved via input-output requests (IOs) to media. The ERRV component is configured to return the read request before all IOs have completed based on a predefined policy. Prior to returning the read, the ERRV component may unmap unfilled pages of the scatter-gather array until data for the unmapped pages becomes available when IOs to the external media complete. Later accesses to unmapped pages will generate page faults, which are handled by stunning the VMs from which the access requests originated until, e.g., all elements of the SG array are filled and all pages of the SG array are mapped.
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