[libvirt] [PATCH 2/2] Add support for preallocated memory - xml2argv
Martin Kletzander
mkletzan at redhat.com
Thu Jun 23 13:42:00 UTC 2016
On Thu, Jun 23, 2016 at 01:25:29PM +0100, Jaroslav Safka wrote:
>Add conversion from xml to argv for subelements
>source,access and allocation of <memoryBacking>
>
>This change introduces support for preallocated
>shared file descriptor based memory backing.
>It allows vhost-user to be used without hugepages.
>
How does this show up in the guest?
>Configured by these elements:
><memoryBacking>
> <source type="file|anonymous"/>
> <access Mode="shared|private"/>
> <allocation mode="immediate|ondemand"/>
></memoryBacking>
>---
> src/qemu/qemu_command.c | 56 ++++++++++++++++++++++
> src/qemu/qemu_command.h | 4 ++
> .../qemuxml2argv-memorybacking-set.args | 6 ++-
> tests/qemuxml2argvtest.c | 3 ++
> 4 files changed, 68 insertions(+), 1 deletion(-)
>
>diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
>index 6944129..321e71f 100644
>--- a/src/qemu/qemu_command.c
>+++ b/src/qemu/qemu_command.c
>@@ -9328,6 +9328,9 @@ qemuBuildCommandLine(virQEMUDriverPtr driver,
> if (qemuBuildNVRAMCommandLine(cmd, def, qemuCaps) < 0)
> goto error;
>
>+ if (qemuBuildMemoryBackendCommandLine(cmd, def, qemuCaps) < 0)
>+ goto error;
>+
So this is not accounted for in any of the memory sizes, right?
Shouldn't this be reflected in some of those virDomainDefGetMemory*()
functions? It probably depends on the answer to my previous question.
> if (snapshot)
> virCommandAddArgList(cmd, "-loadvm", snapshot->def->name, NULL);
>
>@@ -9592,3 +9595,56 @@ qemuBuildChrDeviceStr(char **deviceStr,
>
> return ret;
> }
>+
>+static char *
>+qemuBuildMemoryBackendFileStr(const virDomainDef *def)
>+{
>+ virBuffer buf = VIR_BUFFER_INITIALIZER;
>+ const char template[] = "memory-backend-file,id=mem,size=1024M,mem-path=/var/lib/libvirt/qemu";
>+
Wow, this seems highly configurable. How come none of these options
needs to be changed? That doesn't seem right.
>+ if (VIR_DOMAIN_MEMORY_ACCESS_SHARED == def->mem.access) {
As you might've noticed in the code, we don't do yoda conditions.
>+ // add ",share=on" to -object memory-backend-file
>+ virBufferAsprintf(&buf, "%s,share=on", template);
>+ } else {
>+ virBufferAsprintf(&buf, "%s", template);
>+ }
>+
The virAsprintf() function should shorten this function a bit.
>+
>+ if (virBufferCheckError(&buf) < 0)
>+ goto error;
>+
>+ return virBufferContentAndReset(&buf);
>+
>+ error:
>+ virBufferFreeAndReset(&buf);
>+ return NULL;
>+}
>+
>+
>+int
>+qemuBuildMemoryBackendCommandLine(virCommandPtr cmd,
>+ const virDomainDef *def,
>+ virQEMUCapsPtr qemuCaps __attribute__((unused)))
>+{
>+ char *optstr = NULL;
>+
>+ if (VIR_DOMAIN_MEMORY_ALLOCATION_IMMEDIATE == def->mem.allocation) {
>+ // add '-mem-prealloc'
>+ virCommandAddArg(cmd, "-mem-prealloc");
>+ }
>+
>+ if (VIR_DOMAIN_MEMORY_SOURCE_FILE == def->mem.source) {
>+ optstr = qemuBuildMemoryBackendFileStr(def);
>+ if (optstr) {
>+ virCommandAddArg(cmd, "-object");
>+ virCommandAddArg(cmd, optstr);
>+ VIR_FREE(optstr);
>+ }
>+
>+ // add '-object memory-backend-file,id=mem,size=1024M,mem-path=/var/lib/libvirt/qemu'
>+ // add '-numa node,memdev=mem'
>+ virCommandAddArgList(cmd, "-numa", "node,memdev=mem", NULL);
This looks like it duplicates some of the code that is there already.
Couldn't this be handled more cleanly? Could there be only part of that
memory shared and not all of it?
>+ }
>+
>+ return 0;
>+}
>diff --git a/src/qemu/qemu_command.h b/src/qemu/qemu_command.h
>index 9ff4edb..f95d0ea 100644
>--- a/src/qemu/qemu_command.h
>+++ b/src/qemu/qemu_command.h
>@@ -175,5 +175,9 @@ bool qemuCheckCCWS390AddressSupport(const virDomainDef *def,
> virDomainDeviceInfo info,
> virQEMUCapsPtr qemuCaps,
> const char *devicename);
>+int
>+qemuBuildMemoryBackendCommandLine(virCommandPtr cmd,
>+ const virDomainDef *def,
>+ virQEMUCapsPtr qemuCaps);
>
Not aligned.
> #endif /* __QEMU_COMMAND_H__*/
>diff --git a/tests/qemuxml2argvdata/qemuxml2argv-memorybacking-set.args b/tests/qemuxml2argvdata/qemuxml2argv-memorybacking-set.args
>index bb702dc..626fb21 100644
>--- a/tests/qemuxml2argvdata/qemuxml2argv-memorybacking-set.args
>+++ b/tests/qemuxml2argvdata/qemuxml2argv-memorybacking-set.args
>@@ -19,4 +19,8 @@ QEMU_AUDIO_DRV=none \
> -usb \
> -drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
> -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
>--device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
>+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
>+-mem-prealloc \
>+-object memory-backend-file,id=mem,size=1024M,mem-path=/var/lib/libvirt/qemu,\
So the only difference to setting this up with hugepages is that the
mem-path is not set to hugetlbfs mountpoint?
>+share=on \
>+-numa node,memdev=mem
And it automatically implies numa node? If the numa node is there
automatically (which could be), why not just using the:
<cpu>
<numa>
<cell ... memAccess='shared'/>?
More info on:
https://libvirt.org/formatdomain.html#elementsCPU
Hope that helps, have a nice day,
Martin
>diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
>index a4b8bf4..401b455 100644
>--- a/tests/qemuxml2argvtest.c
>+++ b/tests/qemuxml2argvtest.c
>@@ -2024,6 +2024,9 @@ mymain(void)
>
> DO_TEST("acpi-table", NONE);
>
>+ DO_TEST("memorybacking-unset", NONE);
>+ DO_TEST("memorybacking-set", NONE);
>+
> qemuTestDriverFree(&driver);
>
> return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
>--
>2.1.0
>
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