Re: [libvirt] [PATCH v2 5/5] qemu: Enable memory-backend-file.discard-data whenever possible
On Tue, Apr 17, 2018 at 01:16:42PM +0200, Michal Privoznik wrote:
https://bugzilla.redhat.com/show_bug.cgi?id=1480668
The cases when we cannot enable this optimization are:
1) nvdimms
2) if memAccess='shared'
The specific use case for discard-data=on uses share=on, see:
https://bugzilla.redhat.com/show_bug.cgi?id=1460848#c4
It looks like this will require a explicit XML element, after
all.
Otherwise it is safe to enable it.
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
---
src/qemu/qemu_command.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 527a35779d..b920f5c3e4 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -3121,6 +3121,13 @@ qemuBuildMemoryBackendStr(virJSONValuePtr *backendProps,
NULL) < 0)
goto cleanup;
+ if (!mem->nvdimmPath && memAccess != VIR_DOMAIN_MEMORY_ACCESS_SHARED
&&
+ virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_FILE_DISCARD) &&
+ virJSONValueObjectAdd(props,
+ "B:discard-data", true,
+ NULL) < 0)
+ goto cleanup;
+
switch (memAccess) {
case VIR_DOMAIN_MEMORY_ACCESS_SHARED:
if (virJSONValueObjectAdd(props, "b:share", true, NULL) < 0)
--
2.16.1
--
Eduardo