* UNIX is a trademark of AT&T Bell Laboratories.

** Samuel J. Leffler is currently employed by: Silicon Graphics, Inc.

This work was done under grants from the National Science Foundation under grant MCS80-05144, and the Defense Advance Research Projects Agency (DoD) under ARPA Order No. 4031 monitored by Naval Electronic System Command under Contract No. N00039-82-C-0235.

*** VAX, MASSBUS, UNIBUS, and DEC are trademarks of Digital Equipment Corporation.

[1]  [note 2] The standard trace facilities distributed with 4.2 differ slightly from those described here. The time stamp in the distributed system is calculated from the kernel's time of day variable instead of the VAX hardware register, and the buffer cache trace points do not record the transfer size.

[3]  [note 4] During part of these observations the machine had only four megabytes of memory.

[5]  [note 6] These tests should also have measured the cost of expanding the text segment; unfortunately time did not permit running additional tests.

[7]  [note 8] We assume that a VAX-11/750 runs at 60% of the speed of a VAX-11/780 (not considering floating point operations).

[9]  [note 10] It is not possible to check the input silos at the time of the actual clock interrupt without modifying the terminal line disciplines, as the input queues may not be in a consistent state [note 11] .

[13]  [note 14] The 4.1BSD system used for testing was really a 4.1a system configured with networking facilities and code to support remote file access. The 4.2BSD system also included the remote file access code. Since both systems would be larger than similarly configured ``vanilla'' 4.1BSD or 4.2BSD system, we consider out conclusions to still be valid.

[15]  [note 16] Inode is an abbreviation for ``Index node''. Each file on the system is described by an inode; the inode maintains access permissions, and an array of pointers to the disk blocks that hold the data associated with the file.

[16]  [note 17] The cache is keyed in[equation] the directAssentry in the in

[17]  [note 18] When all the numbers have been exhausted, all capabilities are purged and numbering starts [equation] rPurging is p[equation]

[18]  ** Ethernet is a trademark Xer