On Sun, Jan 26, 2003 at 12:40:19AM +0000, Nicholas Clark wrote:
> On Sat, Jan 25, 2003 at 11:43:40PM +0000, Dave Mitchell wrote:
> > Okay, I just ran a program on a a Solaris machines that mmaps in each
> > of 571 man files 20 times (a total of 11420 mmaps). The process size
> > was 181Mb, but the total system swap available only decreased by 1.2Mb
> > (since files mmapped in RO effecctively don't consume swap).
>
> 11420 simultaneous mmaps in the same process? (just checking that I
> understand you)
yep, exactly that. Src code included below.
> Maybe I'm paranoid (or even plain wrong) but we (parrot) can handle it
> if an mmap fails - we just automatically fall back to plain file loading.
> Can dlopen() cope if an mmap fails? Or on a platform which can only
> do a limited number of mmaps do we run the danger of exhausting them early
> with all our bytecode segments, and then the first time someone attempts
> a require POSIX; it fails because the perl6 DynaLoader can't dlopen
> POSIX.so? (And by then we've done our could-have-been-plain-loaded
> mmaps, so it's too late to adapt)
If there's such a platform, then presumably we don't bother mmap at all
for that platform.
to run: cd to a man directory, then C</tmp/foo *>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
main(int argc, char *argv[])
{
int i,j;
int fd;
off_t size;
void *p;
struct stat st;
for (j=0; j<20; j++) {
for (i=1; i<argc; i++) {
fd = open(argv[i], O_RDONLY);
if (fd == -1) {
perror("open"); exit(1);
}
if (fstat(fd, &st) == -1) {
perror("fstat"); exit(1);
}
size = st.st_size;
/* printf("%d %5d %s\n", i, size, argv[i]); */
p = mmap(0, size, PROT_READ, MAP_SHARED, fd, 0);
if (p < 0) {
perror("mmap"); exit(1);
}
close(fd);
}
printf("done loop %d\n",j);
}
sleep(1000);
}
--
"But Sidley Park is already a picture, and a most amiable picture too.
The slopes are green and gentle. The trees are companionably grouped at
intervals that show them to advantage. The rill is a serpentine ribbon
unwound from the lake peaceably contained by meadows on which the right
amount of sheep are tastefully arranged." Lady Croom - Arcadia
