> I'm observing *excessive high* number of pagefaults
> after a process has forked.
Btw: I'm observing a similar / the same problem with mprotect(2):
# cat mapp.c
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>
#define PAGESIZE 4096
int
main(int argc, char **argv)
{
int fd;
char *filename;
char data_tmp[PAGESIZE];
void *data;
char tmp;
fd = open(filename = "/tmp/data", O_RDWR|O_TRUNC|O_CREAT, 0666);
if (fd < 0) {
perror(filename);
exit(1);
}
memset(data_tmp, '*', sizeof(data_tmp));
write(fd, data_tmp, sizeof(data_tmp));
data = mmap((void*)0x41002000, PAGESIZE, PROT_READ,
MAP_FIXED|MAP_SHARED, fd, 0);
if (data == MAP_FAILED) {
perror("mmap");
exit(1);
}
tmp = *(char*)data;
mprotect(data, PAGESIZE, PROT_READ|PROT_WRITE);
*(char*)data = tmp;
close(fd);
exit(0);
}
This program should produce two pagefaults for address 0x41002000;
but when I just ran it on a gentoo 32-bit dom0 with xen 3.2.0 pae
hypervisor, in a snv_81 domU, the test program was running for
45 seconds and produced almost six million pagefaults for
address 41002000.
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