Hi tech@,
(I post it here as this is a low level tech question. Any extended talk
should be moved to misc@..)
Any way I try to mmap /dev/rsd0c , I get EINVAL (22).
Neither http://man.openbsd.org/mmap nor http://man.openbsd.org/sd gives
any hint.
"ls -l /dev/rsd0c; ls -l /dev/sd0c" shows that sd0c is a block device
and rsd0c is a character device, and mmap's man page says that
"character special files" are OK.
read() speed on /dev/rsd0c is way higher than on /dev/sd0c (in the
ballpark of >>100% faster), that's why I was interested in this in the
first place.
Is it possible to do any way?
Thanks,
Tinker
Example trymap.c below:
# gcc -o trymap trymap.c
# ./trymap /dev/sd0c
Opened /dev/sd0c with handle 3.
mmap succeeded.
# ./trymap /dev/rsd0c
Opened /dev/rsd0c with handle 3.
mmap failed, errno 22: Invalid argument.
Changing to O_RDWR and PROT_READ | PROT_WRITE changes nothing.
Changing flags to MAP_FILE | MAP_SHARED also changes nothing.
trymap.c:
#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <errno.h>
#include <string.h>
int main(int argc, char *argv[]) {
if (argc != 2) { printf("Use: trymap filename\n"); return 0; }
char* filename = argv[1];
int f = open(filename,O_RDONLY);
if (f == -1) {
printf("Failed to open file %s!\n",filename);
return -1;
}
printf("Opened %s with handle %i.\n",filename,f);
void* mmaparea = mmap(NULL, /* addr - we don't provide any suggestion.
*/
1 * 1024 * 1024 * 1024, // 1GB
PROT_READ,
0, /* flags - MAP_FILE implied */
f,
0 // offset
);
if (mmaparea == MAP_FAILED) {
printf("mmap failed, errno %i: %s.\n",errno,strerror(errno));
return -1;
}
printf("mmap succeeded.\n");
return 0;
}
