Commit c658764d authored by Michal Privoznik's avatar Michal Privoznik
Browse files

qemu: Don't use -mem-prealloc among with .prealloc=yes

https://bugzilla.redhat.com/show_bug.cgi?id=1624223



There are two ways to request memory preallocation on cmd line:
-mem-prealloc and .prealloc attribute for a memory-backend-file.
However, as it turns out it's not safe to use both at the same
time. If -mem-prealloc is used then qemu will fully allocate the
memory (this is done by actually touching every page that has
been allocated). Then, if .prealloc=yes is specified,
mbind(flags = MPOL_MF_STRICT | MPOL_MF_MOVE) is called which:

a) has to (possibly) move the memory to a different NUMA node,
b) can have no effect when hugepages are in play (thus ignoring user
request to place memory on desired NUMA nodes).

Prefer -mem-prealloc as it is more backward compatible
compared to switching to "-numa node,memdev=  + -object
memory-backend-file".
Signed-off-by: Michal Privoznik's avatarMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: John Ferlan's avatarJohn Ferlan <jferlan@redhat.com>
parent 9923584c
......@@ -3357,11 +3357,13 @@ qemuBuildMemoryBackendProps(virJSONValuePtr *backendProps,
if (mem->nvdimmPath) {
if (VIR_STRDUP(memPath, mem->nvdimmPath) < 0)
goto cleanup;
prealloc = true;
if (!priv->memPrealloc)
prealloc = true;
} else if (useHugepage) {
if (qemuGetDomainHupageMemPath(def, cfg, pagesize, &memPath) < 0)
goto cleanup;
prealloc = true;
if (!priv->memPrealloc)
prealloc = true;
} else {
/* We can have both pagesize and mem source. If that's the case,
* prefer hugepages as those are more specific. */
......@@ -7576,7 +7578,8 @@ qemuBuildSmpCommandLine(virCommandPtr cmd,
static int
qemuBuildMemPathStr(virQEMUDriverConfigPtr cfg,
const virDomainDef *def,
virCommandPtr cmd)
virCommandPtr cmd,
qemuDomainObjPrivatePtr priv)
{
const long system_page_size = virGetSystemPageSizeKB();
char *mem_path = NULL;
......@@ -7598,8 +7601,10 @@ qemuBuildMemPathStr(virQEMUDriverConfigPtr cfg,
return 0;
}
if (def->mem.allocation != VIR_DOMAIN_MEMORY_ALLOCATION_IMMEDIATE)
if (def->mem.allocation != VIR_DOMAIN_MEMORY_ALLOCATION_IMMEDIATE) {
virCommandAddArgList(cmd, "-mem-prealloc", NULL);
priv->memPrealloc = true;
}
virCommandAddArgList(cmd, "-mem-path", mem_path, NULL);
VIR_FREE(mem_path);
......@@ -7612,7 +7617,8 @@ static int
qemuBuildMemCommandLine(virCommandPtr cmd,
virQEMUDriverConfigPtr cfg,
const virDomainDef *def,
virQEMUCapsPtr qemuCaps)
virQEMUCapsPtr qemuCaps,
qemuDomainObjPrivatePtr priv)
{
if (qemuDomainDefValidateMemoryHotplug(def, qemuCaps, NULL) < 0)
return -1;
......@@ -7631,15 +7637,17 @@ qemuBuildMemCommandLine(virCommandPtr cmd,
virDomainDefGetMemoryInitial(def) / 1024);
}
if (def->mem.allocation == VIR_DOMAIN_MEMORY_ALLOCATION_IMMEDIATE)
if (def->mem.allocation == VIR_DOMAIN_MEMORY_ALLOCATION_IMMEDIATE) {
virCommandAddArgList(cmd, "-mem-prealloc", NULL);
priv->memPrealloc = true;
}
/*
* Add '-mem-path' (and '-mem-prealloc') parameter here if
* the hugepages and no numa node is specified.
*/
if (!virDomainNumaGetNodeCount(def->numa) &&
qemuBuildMemPathStr(cfg, def, cmd) < 0)
qemuBuildMemPathStr(cfg, def, cmd, priv) < 0)
return -1;
if (def->mem.locked && !virQEMUCapsGet(qemuCaps, QEMU_CAPS_REALTIME_MLOCK)) {
......@@ -7748,7 +7756,7 @@ qemuBuildNumaArgStr(virQEMUDriverConfigPtr cfg,
}
if (!needBackend &&
qemuBuildMemPathStr(cfg, def, cmd) < 0)
qemuBuildMemPathStr(cfg, def, cmd, priv) < 0)
goto cleanup;
for (i = 0; i < ncells; i++) {
......@@ -10441,7 +10449,7 @@ qemuBuildCommandLine(virQEMUDriverPtr driver,
if (!migrateURI && !snapshot && qemuDomainAlignMemorySizes(def) < 0)
goto error;
if (qemuBuildMemCommandLine(cmd, cfg, def, qemuCaps) < 0)
if (qemuBuildMemCommandLine(cmd, cfg, def, qemuCaps, priv) < 0)
goto error;
if (qemuBuildSmpCommandLine(cmd, def) < 0)
......
......@@ -1944,6 +1944,8 @@ qemuDomainObjPrivateDataClear(qemuDomainObjPrivatePtr priv)
VIR_FREE(priv->libDir);
VIR_FREE(priv->channelTargetDir);
priv->memPrealloc = false;
/* remove automatic pinning data */
virBitmapFree(priv->autoNodeset);
priv->autoNodeset = NULL;
......@@ -2489,6 +2491,9 @@ qemuDomainObjPrivateXMLFormat(virBufferPtr buf,
if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_BLOCKDEV))
virBufferAsprintf(buf, "<nodename index='%llu'/>\n", priv->nodenameindex);
if (priv->memPrealloc)
virBufferAddLit(buf, "<memPrealloc/>\n");
if (qemuDomainObjPrivateXMLFormatBlockjobs(buf, vm) < 0)
return -1;
......@@ -2993,6 +2998,8 @@ qemuDomainObjPrivateXMLParse(xmlXPathContextPtr ctxt,
goto error;
}
priv->memPrealloc = virXPathBoolean("boolean(./memPrealloc)", ctxt) == 1;
return 0;
error:
......
......@@ -372,6 +372,9 @@ struct _qemuDomainObjPrivate {
/* true if libvirt remembers the original owner for files */
bool rememberOwner;
/* true if global -mem-prealloc appears on cmd line */
bool memPrealloc;
};
# define QEMU_DOMAIN_PRIVATE(vm) \
......
......@@ -13,7 +13,7 @@ QEMU_AUDIO_DRV=none \
-mem-prealloc \
-mem-path /dev/hugepages2M/libvirt/qemu/-1-fedora \
-numa node,nodeid=0,cpus=0-1,mem=1024 \
-object memory-backend-file,id=memdimm0,prealloc=yes,\
-object memory-backend-file,id=memdimm0,\
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 \
......
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