[5314] in Athena Bugs
kernel text cache
daemon@ATHENA.MIT.EDU (John Carr)
Wed Jun 27 04:55:25 1990
To: bugs@ATHENA.MIT.EDU
Date: Wed, 27 Jun 90 04:55:11 EDT
From: John Carr <jfc@ATHENA.MIT.EDU>
The kernel text cache is disabled in release 7.0. This is a bug. Every time
a program is run, if another copy is not running at the same time, the entire
contents of the program must be read from the filesystem. Usually, this is a
remote filesystem. With the text cache enabled, a copy of program text is
usually (58% of the time on my workstation, 82% of the time on another machine
I checked) found in swap space or in RAM, and only the data segment need be
loaded from the filesystem. This is at least a factor of 5 difference in
filesystem I/O for programs with cached text segments.
(I mentioned this during the test period; apparently release engineering
thought it better to ignore than debate this problem.)
