CVS commit: src/usr.bin/make

["Roland Illig" <rillig%netbsd.org@localhost>]

Module Name:    src
Committed By:   rillig
Date:           Mon Dec 28 15:21:33 UTC 2020

Modified Files:
        src/usr.bin/make: parse.c

Log Message:
make(1): remove mmap for loading files, only allow files < 1 GiB

Using mmap is beneficial if the loaded data is read-only, or if it is
accessed in random order.  Neither of these applies here.  When loading
a file, make reads it strictly from top to bottom, once.  During
parsing, the loaded data is modified in-place to insert '\0' and '\n'
for terminating strings and lines.  Because of all of this, there is no
benefit in using mmap.

Reading the file using 2 calls to read(2) (one for the data, one for
checking for EOF) loads the data in a single pass, instead of producing
a page fault whenever the parser passes another page boundary.

Use a Buffer for loading the file data, to avoid calling bmake_realloc
directly.

Do not resize the loaded buffer at the end.  Each loaded file is
short-lived anyway, and only a few files are loaded at the same time, so
there is no point in optimizing this part for low memory usage.


To generate a diff of this commit:
cvs rdiff -u -r1.521 -r1.522 src/usr.bin/make/parse.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.