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Use mmap() in place of posix_memalign() to allocate Lisp memory

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posix_memalign() does not guarantee initializing the allocated
  memory to zero, which Lisp expects, so the code must memset() the
  entire allocated region to zero.  The effect of this is (generally) to
  force the allocation of RAM to the process, which is wasteful, since
  we normally start with only 4% of 256 MB in use for a full.sysout.
  Allocating memory with mmap, using MAP_ANON, guarantees that the
  memory is already zeroed (effectively mapping /dev/zero with copy-on-write)
  so it is not necessary to touch it before use.  This keeps the
  pre-allocated RAM to a minimum.
This commit is contained in:
Nick Briggs 2022-08-31 12:42:39 -07:00
parent 51fffe5827
commit 2b270e6697
1 changed files with 4 additions and 4 deletions
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8
src/ldsout.c
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@ -13,8 +13,9 @@
#include <fcntl.h> // for open, O_RDONLY
#include <stdio.h> // for perror, fprintf, printf, stderr, sprintf
#include <stdlib.h> // for exit, free, malloc, posix_memalign
#include <stdlib.h> // for exit, free, malloc
#include <string.h> // for memset
#include <sys/mman.h> // for mmap
#include <sys/stat.h> // for stat, fstat
#include <unistd.h> // for lseek, read, close, getpagesize
#include "adr68k.h" // for Addr68k_from_LADDR
@ -172,12 +173,11 @@ int sysout_loader(const char *sysout_file_name, int sys_size) {
/* allocate Virtual Memory Space */
if (posix_memalign((void *)&lispworld_scratch, getpagesize(), sys_size * MBYTE) != 0) {
lispworld_scratch = mmap(0, sys_size * MBYTE, PROT_READ|PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
if (lispworld_scratch == MAP_FAILED) {
fprintf(stderr, "sysout_loader: can't allocate Lisp %dMBytes VM \n", sys_size);
exit(-1);
}
/* Sadly, parts of the system depend on memory being initialized to zero */
memset(lispworld_scratch, 0, sys_size * MBYTE);
/* now you can access lispworld */
Lisp_world = (DLword *)lispworld_scratch;