[libvirt] [PATCH v5 7/7] qemu: Implement memoryBacking/discard

https://bugzilla.redhat.com/show_bug.cgi?id=1480668 QEMU has this new feature memory-backend-file.discard-data=yes which is a nifty optimization. Basically, when qemu is quitting or on memory hotplug it calls munmap() and close() on the file that is backing the memory. However, this does not mean kernel won't stop touching that part of memory. It still might. With this feature enabled we tell kernel: "we don't need this memory nor data stored in it". This makes kernel drop the memory immediately without trying to sync memory with the mapped file. Unfortunately, this cannot be turned on by default because we can't be sure when users really don't care about what happens to data after qemu dies. So it has to be opt-in. As usual, there are three places where one can configure memory attributes. This patch adds the feature to all of them. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/qemu/qemu_command.c | 27 ++++++++++++++++++++++++--- tests/qemuxml2argvdata/hugepages-pages.args | 12 ++++++------ tests/qemuxml2argvdata/hugepages-pages3.args | 3 ++- tests/qemuxml2argvdata/hugepages-pages7.args | 3 ++- tests/qemuxml2argvtest.c | 9 ++++++--- 5 files changed, 40 insertions(+), 14 deletions(-) diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 81a9811d14..11ad77f145 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -3029,6 +3029,7 @@ qemuBuildMemoryBackendStr(virJSONValuePtr *backendProps, unsigned long long pagesize = mem->pagesize; bool needHugepage = !!pagesize; bool useHugepage = !!pagesize; + int discard = mem->discard; /* The difference between @needHugepage and @useHugepage is that the latter * is true whenever huge page is defined for the current memory cell. @@ -3039,8 +3040,7 @@ qemuBuildMemoryBackendStr(virJSONValuePtr *backendProps, *backendProps = NULL; *backendType = NULL; - if (memAccess == VIR_DOMAIN_MEMORY_ACCESS_DEFAULT && - mem->targetNode >= 0) { + if (mem->targetNode >= 0) { /* memory devices could provide a invalid guest node */ if (mem->targetNode >= virDomainNumaGetNodeCount(def->numa)) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, @@ -3050,12 +3050,19 @@ qemuBuildMemoryBackendStr(virJSONValuePtr *backendProps, return -1; } - memAccess = virDomainNumaGetNodeMemoryAccessMode(def->numa, mem->targetNode); + if (memAccess == VIR_DOMAIN_MEMORY_ACCESS_DEFAULT) + memAccess = virDomainNumaGetNodeMemoryAccessMode(def->numa, mem->targetNode); + + if (discard == VIR_TRISTATE_BOOL_ABSENT) + discard = virDomainNumaGetNodeDiscard(def->numa, mem->targetNode); } if (memAccess == VIR_DOMAIN_MEMORY_ACCESS_DEFAULT) memAccess = def->mem.access; + if (discard == VIR_TRISTATE_BOOL_ABSENT) + discard = def->mem.discard; + if (virDomainNumatuneGetMode(def->numa, mem->targetNode, &mode) < 0 && virDomainNumatuneGetMode(def->numa, -1, &mode) < 0) mode = VIR_DOMAIN_NUMATUNE_MEM_STRICT; @@ -3143,6 +3150,20 @@ qemuBuildMemoryBackendStr(virJSONValuePtr *backendProps, NULL) < 0) goto cleanup; + if (!mem->nvdimmPath && + discard == VIR_TRISTATE_BOOL_YES) { + if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_FILE_DISCARD)) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("this QEMU doesn't support memory discard")); + goto cleanup; + } + + if (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) diff --git a/tests/qemuxml2argvdata/hugepages-pages.args b/tests/qemuxml2argvdata/hugepages-pages.args index 7ece0272a0..b52cd581d5 100644 --- a/tests/qemuxml2argvdata/hugepages-pages.args +++ b/tests/qemuxml2argvdata/hugepages-pages.args @@ -11,20 +11,20 @@ QEMU_AUDIO_DRV=none \ -m 4096 \ -smp 4,sockets=4,cores=1,threads=1 \ -object memory-backend-file,id=ram-node0,prealloc=yes,\ -mem-path=/dev/hugepages1G/libvirt/qemu/-1-QEMUGuest1,size=1073741824,\ -host-nodes=0-3,policy=bind \ +mem-path=/dev/hugepages1G/libvirt/qemu/-1-QEMUGuest1,discard-data=yes,\ +size=1073741824,host-nodes=0-3,policy=bind \ -numa node,nodeid=0,cpus=0,memdev=ram-node0 \ -object memory-backend-file,id=ram-node1,prealloc=yes,\ mem-path=/dev/hugepages2M/libvirt/qemu/-1-QEMUGuest1,size=1073741824,\ host-nodes=0-3,policy=bind \ -numa node,nodeid=1,cpus=1,memdev=ram-node1 \ -object memory-backend-file,id=ram-node2,prealloc=yes,\ -mem-path=/dev/hugepages1G/libvirt/qemu/-1-QEMUGuest1,size=1073741824,\ -host-nodes=0-3,policy=bind \ +mem-path=/dev/hugepages1G/libvirt/qemu/-1-QEMUGuest1,discard-data=yes,\ +size=1073741824,host-nodes=0-3,policy=bind \ -numa node,nodeid=2,cpus=2,memdev=ram-node2 \ -object memory-backend-file,id=ram-node3,prealloc=yes,\ -mem-path=/dev/hugepages1G/libvirt/qemu/-1-QEMUGuest1,size=1073741824,\ -host-nodes=3,policy=bind \ +mem-path=/dev/hugepages1G/libvirt/qemu/-1-QEMUGuest1,discard-data=yes,\ +size=1073741824,host-nodes=3,policy=bind \ -numa node,nodeid=3,cpus=3,memdev=ram-node3 \ -uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \ -display none \ diff --git a/tests/qemuxml2argvdata/hugepages-pages3.args b/tests/qemuxml2argvdata/hugepages-pages3.args index 2fc701ca22..d55265cdd8 100644 --- a/tests/qemuxml2argvdata/hugepages-pages3.args +++ b/tests/qemuxml2argvdata/hugepages-pages3.args @@ -13,7 +13,8 @@ QEMU_AUDIO_DRV=none \ -object memory-backend-ram,id=ram-node0,size=268435456 \ -numa node,nodeid=0,cpus=0,memdev=ram-node0 \ -object memory-backend-file,id=ram-node1,prealloc=yes,\ -mem-path=/dev/hugepages1G/libvirt/qemu/-1-SomeDummyHugepagesGu,size=805306368 \ +mem-path=/dev/hugepages1G/libvirt/qemu/-1-SomeDummyHugepagesGu,\ +discard-data=yes,size=805306368 \ -numa node,nodeid=1,cpus=1,memdev=ram-node1 \ -uuid ef1bdff4-27f3-4e85-a807-5fb4d58463cc \ -display none \ diff --git a/tests/qemuxml2argvdata/hugepages-pages7.args b/tests/qemuxml2argvdata/hugepages-pages7.args index 1cb598d692..02a98026eb 100644 --- a/tests/qemuxml2argvdata/hugepages-pages7.args +++ b/tests/qemuxml2argvdata/hugepages-pages7.args @@ -18,7 +18,8 @@ mem-path=/dev/hugepages1G/libvirt/qemu/-1-fedora,size=1073741824,\ host-nodes=1-3,policy=bind \ -device pc-dimm,node=0,memdev=memdimm0,id=dimm0,slot=0 \ -object memory-backend-file,id=memdimm1,prealloc=yes,\ -mem-path=/dev/hugepages2M/libvirt/qemu/-1-fedora,share=no,size=536870912 \ +mem-path=/dev/hugepages2M/libvirt/qemu/-1-fedora,discard-data=yes,share=no,\ +size=536870912 \ -device pc-dimm,node=0,memdev=memdimm1,id=dimm1,slot=1 \ -uuid 63840878-0deb-4095-97e6-fc444d9bc9fa \ -display none \ diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c index 756ca7a77f..d4d64b0d21 100644 --- a/tests/qemuxml2argvtest.c +++ b/tests/qemuxml2argvtest.c @@ -919,11 +919,13 @@ mymain(void) QEMU_CAPS_OBJECT_MEMORY_FILE); DO_TEST("hugepages-pages", QEMU_CAPS_OBJECT_MEMORY_RAM, - QEMU_CAPS_OBJECT_MEMORY_FILE); + QEMU_CAPS_OBJECT_MEMORY_FILE, + QEMU_CAPS_OBJECT_MEMORY_FILE_DISCARD); DO_TEST("hugepages-pages2", QEMU_CAPS_OBJECT_MEMORY_RAM, QEMU_CAPS_OBJECT_MEMORY_FILE); DO_TEST("hugepages-pages3", QEMU_CAPS_OBJECT_MEMORY_RAM, - QEMU_CAPS_OBJECT_MEMORY_FILE); + QEMU_CAPS_OBJECT_MEMORY_FILE, + QEMU_CAPS_OBJECT_MEMORY_FILE_DISCARD); DO_TEST("hugepages-shared", QEMU_CAPS_OBJECT_MEMORY_RAM, QEMU_CAPS_OBJECT_MEMORY_FILE); @@ -933,7 +935,8 @@ mymain(void) DO_TEST("hugepages-pages5", NONE); DO_TEST("hugepages-pages6", NONE); DO_TEST("hugepages-pages7", - QEMU_CAPS_DEVICE_PC_DIMM, QEMU_CAPS_OBJECT_MEMORY_FILE); + QEMU_CAPS_DEVICE_PC_DIMM, QEMU_CAPS_OBJECT_MEMORY_FILE, + QEMU_CAPS_OBJECT_MEMORY_FILE_DISCARD); DO_TEST("hugepages-memaccess", QEMU_CAPS_OBJECT_MEMORY_FILE, QEMU_CAPS_OBJECT_MEMORY_RAM, QEMU_CAPS_DEVICE_PC_DIMM, QEMU_CAPS_NUMA); -- 2.16.1