bdrv_file_open()) */
#define BDRV_O_NOCACHE 0x0020 /* do not use the host page cache */
#define BDRV_O_CACHE_WB 0x0040 /* use write-back caching */
-#define BDRV_O_CACHE_DEF 0x0080 /* use default caching */
-#define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_CACHE_DEF)
+#define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB)
void bdrv_info(Monitor *mon);
void bdrv_info_stats(Monitor *mon);
QCowHeader header;
uint64_t ext_end;
- /* Performance is terrible right now with cache=writethrough due mainly
- * to reference count updates. If the user does not explicitly specify
- * a caching type, force to writeback caching.
- */
- if ((flags & BDRV_O_CACHE_DEF)) {
- flags |= BDRV_O_CACHE_WB;
- flags &= ~BDRV_O_CACHE_DEF;
- }
ret = bdrv_file_open(&s->hd, filename, flags);
if (ret < 0)
return ret;
Some block drivers perform badly with @option{cache=writethrough}, most notably,
qcow2. If performance is more important than correctness,
-@option{cache=writeback} should be used with qcow2. By default, if no explicit
-caching is specified for a qcow2 disk image, @option{cache=writeback} will be
-used. For all other disk types, @option{cache=writethrough} is the default.
+@option{cache=writeback} should be used with qcow2.
Instead of @option{-cdrom} you can use:
@example
unit_id = -1;
translation = BIOS_ATA_TRANSLATION_AUTO;
index = -1;
- cache = 3;
+ cache = 1;
if (machine->use_scsi) {
type = IF_SCSI;
bdrv_flags |= BDRV_O_NOCACHE;
else if (cache == 2) /* write-back */
bdrv_flags |= BDRV_O_CACHE_WB;
- else if (cache == 3) /* not specified */
- bdrv_flags |= BDRV_O_CACHE_DEF;
if (bdrv_open2(bdrv, file, bdrv_flags, drv) < 0) {
fprintf(stderr, "qemu: could not open disk image %s\n",
file);