First-Class User-Level Threads

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First-Class User-Level Threads (1991)

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by Brian D. Marsh , Michael L. Scott , Thomas J. Leblanc , Evangelos P. Markatos

Venue:	In Proceedings of the Thirteenth ACM Symposium on Operating Systems Principles
Citations:	124 - 12 self

BibTeX

@INPROCEEDINGS{Marsh91first-classuser-level,
    author = {Brian D. Marsh and Michael L. Scott and Thomas J. Leblanc and Evangelos P. Markatos},
    title = {First-Class User-Level Threads},
    booktitle = {In Proceedings of the Thirteenth ACM Symposium on Operating Systems Principles},
    year = {1991},
    pages = {110--121}
}

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Abstract

It is often desirable, for reasons of clarity, portability, and efficiency, to write parallel programs in which the number of processes is independent of the number of available processors. Several modern operating systems support more than one process in an address space, but the overhead of creating and synchronizing kernel processes can be high. Many runtime environments implement lightweight processes (threads) in user space, but this approach usually results in second-class status for threads, making it difficult or impossible to perform scheduling operations at appropriate times (e.g. when the current thread blocks in the kernel). In addition, a lack of common assumptions may also make it difficult for parallel programs or library routines that use dissimilar thread packages to communicate with each other, or to synchronize access to shared data. We describe a set of kernel mechanisms and conventions designed to accord first-class status to user-level threads, allowing them to be used in any reasonable way that traditional kernel-provided processes can be used, while leaving the details of their implementation to userlevel code. The key features of our approach are (1) shared memory for asynchronous communication between the kernel and the user, (2) software interrupts for events that might require action on the part of a user-level scheduler, and (3) a scheduler interface convention that facilitates interactions in user space between dissimilar kinds of threads. We have incorporated these mechanisms in the Psyche parallel operating system, and have used them to implement several different kinds of user-level threads. We argue for our approach in terms of both flexibility and performance.

Keyphrases

first-class user-level thread user space user-level thread parallel program system support kernel process key feature dissimilar kind current thread block second-class status kernel mechanism library routine asynchronous communication first-class status several different kind appropriate time scheduler interface convention address space psyche parallel dissimilar thread package available processor user-level scheduler traditional kernel-provided process reasonable way common assumption software interrupt userlevel code

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