Am 08.04.2013 um 10:38 schrieb Paolo Bonzini <pbonz...@redhat.com>:
> Il 06/04/2013 00:06, Peter Lieven ha scritto:
>>>> I think we should MADV_DONTNEED it.
>> i have to correct myself, on Linux it seems that MADV_DONTNEED guarantees
>> that
>> subsequent reads will return a zero filled page.
>>
>> If I am right with that we could MADV_DONTNEED the memory on startup and keep
>> not sending zero pages in bulk stage if we are running under Linux. Am I
>> right with that?
>
> Actually we can use mmap+munmap to allocate a well-aligned, always zero
> block for the RAM.
like this?
diff --git a/exec.c b/exec.c
index 786987a..dfd1ad3 100644
--- a/exec.c
+++ b/exec.c
@@ -1048,27 +1048,31 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size,
void *host,
new_block->host = host;
new_block->flags |= RAM_PREALLOC_MASK;
} else {
- if (mem_path) {
+ if (xen_enabled()) {
+ xen_ram_alloc(new_block->offset, size, mr);
+ memory_try_enable_merging(new_block->host, size);
+ } else {
+ if (mem_path) {
#if defined (__linux__) && !defined(TARGET_S390X)
- new_block->host = file_ram_alloc(new_block, size, mem_path);
- if (!new_block->host) {
- new_block->host = qemu_vmalloc(size);
- memory_try_enable_merging(new_block->host, size);
- }
+ new_block->host = file_ram_alloc(new_block, size, mem_path);
#else
- fprintf(stderr, "-mem-path option unsupported\n");
- exit(1);
+ fprintf(stderr, "-mem-path option unsupported\n");
+ exit(1);
#endif
- } else {
- if (xen_enabled()) {
- xen_ram_alloc(new_block->offset, size, mr);
- } else if (kvm_enabled()) {
+ }
+ if (!new_block->host && kvm_enabled()) {
/* some s390/kvm configurations have special constraints */
new_block->host = kvm_vmalloc(size);
- } else {
- new_block->host = qemu_vmalloc(size);
}
- memory_try_enable_merging(new_block->host, size);
+ if (!new_block->host) {
+ new_block->host = mmap(0, size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+ if (new_block->host == MAP_FAILED) {
+ fprintf(stderr,"qemu_ram_alloc: can't mmap RAM pages
%d\n",errno);
+ exit(1);
+ }
+ memory_try_enable_merging(new_block->host, size);
+ }
}
}
new_block->length = size;
@@ -1142,25 +1146,19 @@ void qemu_ram_free(ram_addr_t addr)
;
} else if (mem_path) {
#if defined (__linux__) && !defined(TARGET_S390X)
+ munmap(block->host, block->length);
if (block->fd) {
- munmap(block->host, block->length);
close(block->fd);
- } else {
- qemu_vfree(block->host);
}
#else
abort();
#endif
} else {
-#if defined(TARGET_S390X) && defined(CONFIG_KVM)
- munmap(block->host, block->length);
-#else
if (xen_enabled()) {
xen_invalidate_map_cache_entry(block->host);
} else {
- qemu_vfree(block->host);
+ munmap(block->host, block->length);
}
-#endif
}
g_free(block);
break;
diff --git a/kvm-all.c b/kvm-all.c
index 9b433d3..90be8e3 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1742,7 +1742,7 @@ void *kvm_vmalloc(ram_addr_t size)
return mem;
}
#endif
- return qemu_vmalloc(size);
+ return NULL;
}
void kvm_setup_guest_memory(void *start, size_t size)
