From af079d99de7c556c3b9bb10037dae90e0f23f38a Mon Sep 17 00:00:00 2001

Message-Id: <af079d99de7c556c3b9bb10037dae90e0f23f38a@dist-git>

From: Michal Privoznik <mprivozn@redhat.com>

Date: Tue, 18 Dec 2018 11:47:36 +0100

Subject: [PATCH] qemu: Don't use -mem-prealloc among with .prealloc=yes

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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 <mprivozn@redhat.com>

Reviewed-by: John Ferlan <jferlan@redhat.com>

(cherry picked from commit c658764decf357ef2a064f09235fb6b8bd027f8b)

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

Conflicts:

src/qemu/qemu_command.c:

src/qemu/qemu_domain.c:

src/qemu/qemu_domain.h: Context mostly, the upstream code

                        diverged.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

Message-Id: <37771aafbb9d1855721efde7ade34c7b98fb1fc7.1545129996.git.mprivozn@redhat.com>

Reviewed-by: Ján Tomko <jtomko@redhat.com>

---

 src/qemu/qemu_command.c                       | 26 ++++++++++++-------

 src/qemu/qemu_domain.c                        |  7 +++++

 src/qemu/qemu_domain.h                        |  3 +++

 .../hugepages-numa-default-dimm.args          |  2 +-

 4 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c

index fa2b904239..7ffc4358e3 100644

--- a/src/qemu/qemu_command.c

+++ b/src/qemu/qemu_command.c

@@ -3185,11 +3185,13 @@ qemuBuildMemoryBackendProps(virJSONValuePtr *backendProps,

         if (useHugepage) {

             if (qemuGetDomainHupageMemPath(def, cfg, pagesize, &memPath) < 0)

                 goto cleanup;

-            prealloc = true;

+            if (!priv->memPrealloc)

+                prealloc = true;

         } else if (mem->nvdimmPath) {

             if (VIR_STRDUP(memPath, mem->nvdimmPath) < 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. */

@@ -7603,7 +7605,8 @@ 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;

@@ -7624,8 +7627,10 @@ qemuBuildMemPathStr(virQEMUDriverConfigPtr cfg,

     if (qemuGetDomainHupageMemPath(def, cfg, def->mem.hugepages[0].size, &mem_path) < 0)

         return -1;

-    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);

@@ -7638,7 +7643,8 @@ static int

 qemuBuildMemCommandLine(virCommandPtr cmd,

                         virQEMUDriverConfigPtr cfg,

                         const virDomainDef *def,

-                        virQEMUCapsPtr qemuCaps)

+                        virQEMUCapsPtr qemuCaps,

+                        qemuDomainObjPrivatePtr priv)

 {

     if (qemuDomainDefValidateMemoryHotplug(def, qemuCaps, NULL) < 0)

         return -1;

@@ -7657,15 +7663,17 @@ 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)) {

@@ -7772,7 +7780,7 @@ qemuBuildNumaArgStr(virQEMUDriverConfigPtr cfg,

     }

     if (!needBackend &&

-        qemuBuildMemPathStr(cfg, def, cmd) < 0)

+        qemuBuildMemPathStr(cfg, def, cmd, priv) < 0)

         goto cleanup;

     for (i = 0; i < ncells; i++) {

@@ -10445,7 +10453,7 @@ 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)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c

index 8604385aa2..95b84af78a 100644

--- a/src/qemu/qemu_domain.c

+++ b/src/qemu/qemu_domain.c

@@ -1936,6 +1936,8 @@ qemuDomainObjPrivateDataClear(qemuDomainObjPrivatePtr priv)

     VIR_FREE(priv->libDir);

     VIR_FREE(priv->channelTargetDir);

+    priv->memPrealloc = false;

+

     /* remove automatic pinning data */

     virBitmapFree(priv->autoNodeset);

     priv->autoNodeset = NULL;

@@ -2439,6 +2441,9 @@ qemuDomainObjPrivateXMLFormat(virBufferPtr buf,

     qemuDomainObjPrivateXMLFormatPR(buf, priv);

+    if (priv->memPrealloc)

+        virBufferAddLit(buf, "<memPrealloc/>\n");

+

     if (qemuDomainObjPrivateXMLFormatBlockjobs(buf, vm) < 0)

         return -1;

@@ -2934,6 +2939,8 @@ qemuDomainObjPrivateXMLParse(xmlXPathContextPtr ctxt,

     if (qemuDomainObjPrivateXMLParseBlockjobs(priv, ctxt) < 0)

         goto error;

+    priv->memPrealloc = virXPathBoolean("boolean(./memPrealloc)", ctxt) == 1;

+

     return 0;

  error:

diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h

index cc406e3ca0..8463a8b706 100644

--- a/src/qemu/qemu_domain.h

+++ b/src/qemu/qemu_domain.h

@@ -367,6 +367,9 @@ struct _qemuDomainObjPrivate {

     /* qemuProcessStartCPUs stores the reason for starting vCPUs here for the

      * RESUME event handler to use it */

     virDomainRunningReason runningReason;

+

+    /* true if global -mem-prealloc appears on cmd line */

+    bool memPrealloc;

 };

 # define QEMU_DOMAIN_PRIVATE(vm) \

diff --git a/tests/qemuxml2argvdata/hugepages-numa-default-dimm.args b/tests/qemuxml2argvdata/hugepages-numa-default-dimm.args

index 855966a137..e7294a0882 100644

--- a/tests/qemuxml2argvdata/hugepages-numa-default-dimm.args

+++ b/tests/qemuxml2argvdata/hugepages-numa-default-dimm.args

@@ -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 \

-- 

2.22.0