Anthony Liguori wrote:
Mark McLoughlin wrote:
And let's take a step back too. If people are really concerned about
this point, let's introduce a sync=on option that opens the image with
O_SYNC. This will effectively make the cache write-through without
the baggage associated with O_DIRECT.
I'm starting to slowly convince myself we should always open files with
O_SYNC. Barriers should just force ordering within the thread pool.
posix-aio has no interface for this but we could create one with our own
thread pool implementation.
Ryan: could you give the following patch a perf-run so we can see how
this would effect us?
Thanks,
Anthony Liguori
While I object to libvirt always setting cache=off, I think sync=on
for IDE and SCSI may be reasonable (you don't want it for virtio-blk
once we implement proper barriers with fdatasync I think).
Regards,
Anthony Liguori
Cheers,
Mark.
diff --git a/block-raw-posix.c b/block-raw-posix.c
index c0404fa..0d8ffdb 100644
--- a/block-raw-posix.c
+++ b/block-raw-posix.c
@@ -121,7 +121,7 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
s->lseek_err_cnt = 0;
- open_flags = O_BINARY;
+ open_flags = O_BINARY | O_SYNC;
if ((flags & BDRV_O_ACCESS) == O_RDWR) {
open_flags |= O_RDWR;
} else {
--
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