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qemu: mempath: prefault pages manually (v4)

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v4: s/fail/failed/  (Peter Maydell)

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Marcelo Tosatti 2013-10-28 18:51:46 -02:00 committed by Paolo Bonzini
parent fb541ca59c
commit ef36fa1492
3 changed files with 47 additions and 18 deletions
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59
exec.c
View File

@ -904,6 +904,13 @@ static long gethugepagesize(const char *path)
return fs.f_bsize;
}
static sigjmp_buf sigjump;
static void sigbus_handler(int signal)
{
siglongjmp(sigjump, 1);
}
static void *file_ram_alloc(RAMBlock *block,
ram_addr_t memory,
const char *path)
@ -913,9 +920,6 @@ static void *file_ram_alloc(RAMBlock *block,
char *c;
void *area;
int fd;
#ifdef MAP_POPULATE
int flags;
#endif
unsigned long hpagesize;
hpagesize = gethugepagesize(path);
@ -963,21 +967,52 @@ static void *file_ram_alloc(RAMBlock *block,
if (ftruncate(fd, memory))
perror("ftruncate");
#ifdef MAP_POPULATE
/* NB: MAP_POPULATE won't exhaustively alloc all phys pages in the case
* MAP_PRIVATE is requested. For mem_prealloc we mmap as MAP_SHARED
* to sidestep this quirk.
*/
flags = mem_prealloc ? MAP_POPULATE | MAP_SHARED : MAP_PRIVATE;
area = mmap(0, memory, PROT_READ | PROT_WRITE, flags, fd, 0);
#else
area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
#endif
if (area == MAP_FAILED) {
perror("file_ram_alloc: can't mmap RAM pages");
close(fd);
return (NULL);
}
if (mem_prealloc) {
int ret, i;
struct sigaction act, oldact;
sigset_t set, oldset;
memset(&act, 0, sizeof(act));
act.sa_handler = &sigbus_handler;
act.sa_flags = 0;
ret = sigaction(SIGBUS, &act, &oldact);
if (ret) {
perror("file_ram_alloc: failed to install signal handler");
exit(1);
}
/* unblock SIGBUS */
sigemptyset(&set);
sigaddset(&set, SIGBUS);
pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
if (sigsetjmp(sigjump, 1)) {
fprintf(stderr, "file_ram_alloc: failed to preallocate pages\n");
exit(1);
}
/* MAP_POPULATE silently ignores failures */
for (i = 0; i < (memory/hpagesize)-1; i++) {
memset(area + (hpagesize*i), 0, 1);
}
ret = sigaction(SIGBUS, &oldact, NULL);
if (ret) {
perror("file_ram_alloc: failed to reinstall signal handler");
exit(1);
}
pthread_sigmask(SIG_SETMASK, &oldset, NULL);
}
block->fd = fd;
return area;
}

2
qemu-options.hx
View File

@ -228,7 +228,6 @@ STEXI
Allocate guest RAM from a temporarily created file in @var{path}.
ETEXI
#ifdef MAP_POPULATE
DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
"-mem-prealloc preallocate guest memory (use with -mem-path)\n",
QEMU_ARCH_ALL)
@ -237,7 +236,6 @@ STEXI
@findex -mem-prealloc
Preallocate memory when using -mem-path.
ETEXI
#endif
DEF("k", HAS_ARG, QEMU_OPTION_k,
"-k language use keyboard layout (for example 'fr' for French)\n",

4
vl.c
View File

@ -188,9 +188,7 @@ static int display_remote;
const char* keyboard_layout = NULL;
ram_addr_t ram_size;
const char *mem_path = NULL;
#ifdef MAP_POPULATE
int mem_prealloc = 0; /* force preallocation of physical target memory */
#endif
int nb_nics;
NICInfo nd_table[MAX_NICS];
int autostart;
@ -3206,11 +3204,9 @@ int main(int argc, char **argv, char **envp)
case QEMU_OPTION_mempath:
mem_path = optarg;
break;
#ifdef MAP_POPULATE
case QEMU_OPTION_mem_prealloc:
mem_prealloc = 1;
break;
#endif
case QEMU_OPTION_d:
log_mask = optarg;
break;