6:38 p.m.
Introduce support for QEMU's new mapped-ram stream format [1].
mapped-ram is enabled by default if the underlying QEMU advertises
the mapped-ram migration capability. It can be disabled by changing
the 'save_image_version' setting in qemu.conf to version '2'.
To use mapped-ram with QEMU:
- The 'mapped-ram' migration capability must be set to true
- The 'multifd' migration capability must be set to true and
the 'multifd-channels' migration parameter must set to 1
- QEMU must be provided an fdset containing the migration fd
- The 'migrate' qmp command is invoked with a URI referencing the
fdset and an offset where to start writing the data stream, e.g.
{"execute":"migrate",
"arguments":{"detach":true,"resume":false,
"uri":"file:/dev/fdset/0,offset=0x11921"}}
The mapped-ram stream, in conjunction with direct IO and multifd
support provided by subsequent patches, can significantly improve
the time required to save VM memory state. The following tables
compare mapped-ram with the existing, sequential save stream. In
all cases, the save and restore operations are to/from a block
device comprised of two NVMe disks in RAID0 configuration with
xfs (~8600MiB/s). The values in the 'save time' and 'restore time'
columns were scraped from the 'real' time reported by time(1). The
'Size' and 'Blocks' columns were provided by the corresponding
outputs of stat(1).
VM: 32G RAM, 1 vcpu, idle (shortly after boot)
| save | restore |
| time | time | Size | Blocks
-----------------------+---------+---------+--------------+--------
legacy | 6.193s | 4.399s | 985744812 | 1925288
-----------------------+---------+---------+--------------+--------
mapped-ram | 5.109s | 1.176s | 34368554354 | 1774472
-----------------------+---------+---------+--------------+--------
legacy + direct IO | 5.725s | 4.512s | 985765251 | 1925328
-----------------------+---------+---------+--------------+--------
mapped-ram + direct IO | 4.627s | 1.490s | 34368554354 | 1774304
-----------------------+---------+---------+--------------+--------
mapped-ram + direct IO | | | |
+ multifd-channels=8 | 4.421s | 0.845s | 34368554318 | 1774312
-------------------------------------------------------------------
VM: 32G RAM, 30G dirty, 1 vcpu in tight loop dirtying memory
| save | restore |
| time | time | Size | Blocks
-----------------------+---------+---------+--------------+---------
legacy | 25.800s | 14.332s | 33154309983 | 64754512
-----------------------+---------+---------+--------------+---------
mapped-ram | 18.742s | 15.027s | 34368559228 | 64617160
-----------------------+---------+---------+--------------+---------
legacy + direct IO | 13.115s | 18.050s | 33154310496 | 64754520
-----------------------+---------+---------+--------------+---------
mapped-ram + direct IO | 13.623s | 15.959s | 34368557392 | 64662040
-----------------------+-------- +---------+--------------+---------
mapped-ram + direct IO | | | |
+ multifd-channels=8 | 6.994s | 6.470s | 34368554980 | 64665776
--------------------------------------------------------------------
As can be seen from the tables, one caveat of mapped-ram is the logical
file size of a saved image is basically equivalent to the VM memory size.
Note however that mapped-ram typically uses fewer blocks on disk.
Another caveat of mapped-ram is the requirement for a seekable file
descriptor, which currently makes it incompatible with libvirt's
support for save image compression. Also note the mapped-ram stream
is incompatible with the existing stream format, hence mapped-ram
cannot be used to restore an image saved with the existing format
and vice versa.
[1]
https://gitlab.com/qemu-project/qemu/-/blob/master/docs/devel/migration/m...
Signed-off-by: Jim Fehlig <jfehlig(a)suse.com>
---
src/qemu/qemu_driver.c | 20 ++++--
src/qemu/qemu_migration.c | 139 ++++++++++++++++++++++++++------------
src/qemu/qemu_migration.h | 4 +-
src/qemu/qemu_monitor.c | 36 ++++++++++
src/qemu/qemu_monitor.h | 4 ++
src/qemu/qemu_saveimage.c | 43 +++++++++---
src/qemu/qemu_saveimage.h | 2 +
src/qemu/qemu_snapshot.c | 9 ++-
8 files changed, 195 insertions(+), 62 deletions(-)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 6c0d3e097c..977763e5d8 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -2617,6 +2617,8 @@ qemuDomainSaveInternal(virQEMUDriver *driver,
qemuDomainObjPrivate *priv = vm->privateData;
virQEMUSaveData *data = NULL;
g_autoptr(qemuDomainSaveCookie) cookie = NULL;
+ g_autoptr(qemuMigrationParams) saveParams = NULL;
+ bool mappedRam = false;
if (virDomainObjBeginAsyncJob(vm, VIR_ASYNC_JOB_SAVE,
VIR_DOMAIN_JOB_OPERATION_SAVE, flags) < 0)
@@ -2683,12 +2685,17 @@ qemuDomainSaveInternal(virQEMUDriver *driver,
if (!(cookie = qemuDomainSaveCookieNew(vm)))
goto endjob;
- if (!(data = virQEMUSaveDataNew(driver, xml, cookie, was_running, compressed)))
+
+ if (!(data = virQEMUSaveDataNew(driver, vm, xml, cookie, was_running, compressed)))
goto endjob;
xml = NULL;
+ mappedRam = data->header.features & QEMU_SAVE_FEATURE_MAPPED_RAM;
+ if (!(saveParams = qemuMigrationParamsForSave(mappedRam)))
+ goto endjob;
+
ret = qemuSaveImageCreate(driver, vm, path, data, compressor,
- flags, VIR_ASYNC_JOB_SAVE);
+ saveParams, flags, VIR_ASYNC_JOB_SAVE);
if (ret < 0)
goto endjob;
@@ -3122,6 +3129,8 @@ doCoreDump(virQEMUDriver *driver,
memory_dump_format) < 0)
goto cleanup;
} else {
+ g_autoptr(qemuMigrationParams) dump_params = NULL;
+
if (dumpformat != VIR_DOMAIN_CORE_DUMP_FORMAT_RAW) {
virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
_("kdump-compressed format is only supported with
memory-only dump"));
@@ -3131,8 +3140,11 @@ doCoreDump(virQEMUDriver *driver,
if (!qemuMigrationSrcIsAllowed(vm, false, VIR_ASYNC_JOB_DUMP, 0))
goto cleanup;
- if (qemuMigrationSrcToFile(driver, vm, fd, compressor,
- VIR_ASYNC_JOB_DUMP) < 0)
+ if (!(dump_params = qemuMigrationParamsNew()))
+ goto cleanup;
+
+ if (qemuMigrationSrcToFile(driver, vm, &fd, compressor,
+ dump_params, dump_flags, VIR_ASYNC_JOB_DUMP) < 0)
goto cleanup;
}
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index c1bdaa273b..3ab5e2fa30 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -6944,46 +6944,17 @@ qemuMigrationProcessUnattended(virQEMUDriver *driver,
}
-/* Helper function called while vm is active. */
-int
-qemuMigrationSrcToFile(virQEMUDriver *driver, virDomainObj *vm,
- int fd,
- virCommand *compressor,
- virDomainAsyncJob asyncJob)
+static int
+qemuMigrationSrcToLegacyFile(virQEMUDriver *driver,
+ virDomainObj *vm,
+ int fd,
+ virCommand *compressor,
+ virDomainAsyncJob asyncJob)
{
qemuDomainObjPrivate *priv = vm->privateData;
- int rc;
int ret = -1;
int pipeFD[2] = { -1, -1 };
- unsigned long saveMigBandwidth = priv->migMaxBandwidth;
char *errbuf = NULL;
- virErrorPtr orig_err = NULL;
- g_autoptr(qemuMigrationParams) migParams = NULL;
-
- if (qemuMigrationSetDBusVMState(driver, vm) < 0)
- return -1;
-
- /* Increase migration bandwidth to unlimited since target is a file.
- * Failure to change migration speed is not fatal. */
- if (!(migParams = qemuMigrationParamsForSave(false)))
- return -1;
-
- if (qemuMigrationParamsSetULL(migParams,
- QEMU_MIGRATION_PARAM_MAX_BANDWIDTH,
- QEMU_DOMAIN_MIG_BANDWIDTH_MAX * 1024 * 1024) < 0)
- return -1;
-
- if (qemuMigrationParamsApply(vm, asyncJob, migParams, 0) < 0)
- return -1;
-
- priv->migMaxBandwidth = QEMU_DOMAIN_MIG_BANDWIDTH_MAX;
-
- if (!virDomainObjIsActive(vm)) {
- virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
- _("guest unexpectedly quit"));
- /* nothing to tear down */
- return -1;
- }
if (compressor && virPipe(pipeFD) < 0)
return -1;
@@ -7000,7 +6971,7 @@ qemuMigrationSrcToFile(virQEMUDriver *driver, virDomainObj *vm,
goto cleanup;
if (!compressor) {
- rc = qemuMonitorMigrateToFd(priv->mon, 0, fd);
+ ret = qemuMonitorMigrateToFd(priv->mon, 0, fd);
} else {
virCommandSetInputFD(compressor, pipeFD[0]);
virCommandSetOutputFD(compressor, &fd);
@@ -7016,12 +6987,99 @@ qemuMigrationSrcToFile(virQEMUDriver *driver, virDomainObj *vm,
qemuDomainObjExitMonitor(vm);
goto cleanup;
}
- rc = qemuMonitorMigrateToFd(priv->mon, 0, pipeFD[1]);
+ ret = qemuMonitorMigrateToFd(priv->mon, 0, pipeFD[1]);
if (VIR_CLOSE(pipeFD[0]) < 0 ||
VIR_CLOSE(pipeFD[1]) < 0)
VIR_WARN("failed to close intermediate pipe");
}
qemuDomainObjExitMonitor(vm);
+
+ cleanup:
+ VIR_FORCE_CLOSE(pipeFD[0]);
+ VIR_FORCE_CLOSE(pipeFD[1]);
+
+ if (errbuf) {
+ VIR_DEBUG("Compression binary stderr: %s", NULLSTR(errbuf));
+ VIR_FREE(errbuf);
+ }
+
+ return ret;
+}
+
+
+static int
+qemuMigrationSrcToMappedFile(virQEMUDriver *driver,
+ virDomainObj *vm,
+ int *fd,
+ unsigned int flags,
+ virDomainAsyncJob asyncJob)
+{
+ int ret;
+
+ /* mapped-ram does not support directIO */
+ if ((flags & VIR_DOMAIN_SAVE_BYPASS_CACHE)) {
+ virReportError(VIR_ERR_OPERATION_FAILED, "%s",
+ _("bypass cache unsupported by this system"));
+ return -1;
+ }
+
+ if (qemuSecuritySetImageFDLabel(driver->securityManager, vm->def, *fd) < 0)
+ return -1;
+
+ if (qemuDomainObjEnterMonitorAsync(vm, asyncJob) < 0)
+ return -1;
+
+ ret = qemuMonitorMigrateToFdSet(vm, 0, fd);
+ qemuDomainObjExitMonitor(vm);
+ return ret;
+}
+
+
+/* Helper function called while vm is active. */
+int
+qemuMigrationSrcToFile(virQEMUDriver *driver, virDomainObj *vm,
+ int *fd,
+ virCommand *compressor,
+ qemuMigrationParams *migParams,
+ unsigned int flags,
+ virDomainAsyncJob asyncJob)
+{
+ qemuDomainObjPrivate *priv = vm->privateData;
+ int rc;
+ int ret = -1;
+ unsigned long saveMigBandwidth = priv->migMaxBandwidth;
+ virErrorPtr orig_err = NULL;
+
+ if (qemuMigrationSetDBusVMState(driver, vm) < 0)
+ return -1;
+
+ /* Increase migration bandwidth to unlimited since target is a file.
+ * Failure to change migration speed is not fatal. */
+ if (migParams &&
+ qemuMigrationParamsSetULL(migParams,
+ QEMU_MIGRATION_PARAM_MAX_BANDWIDTH,
+ QEMU_DOMAIN_MIG_BANDWIDTH_MAX * 1024 * 1024) < 0)
+ return -1;
+
+ if (qemuMigrationParamsApply(vm, asyncJob, migParams, 0) < 0)
+ return -1;
+
+ priv->migMaxBandwidth = QEMU_DOMAIN_MIG_BANDWIDTH_MAX;
+
+ if (!virDomainObjIsActive(vm)) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("guest unexpectedly quit"));
+ /* nothing to tear down */
+ return -1;
+ }
+
+ if (migParams &&
+ qemuMigrationParamsCapEnabled(migParams, QEMU_MIGRATION_CAP_MAPPED_RAM)) {
+ rc = qemuMigrationSrcToMappedFile(driver, vm, fd, flags, asyncJob);
+ } else {
+ rc = qemuMigrationSrcToLegacyFile(driver, vm, *fd, compressor, asyncJob);
+ }
+
if (rc < 0)
goto cleanup;
@@ -7057,13 +7115,6 @@ qemuMigrationSrcToFile(virQEMUDriver *driver, virDomainObj *vm,
priv->migMaxBandwidth = saveMigBandwidth;
}
- VIR_FORCE_CLOSE(pipeFD[0]);
- VIR_FORCE_CLOSE(pipeFD[1]);
- if (errbuf) {
- VIR_DEBUG("Compression binary stderr: %s", NULLSTR(errbuf));
- VIR_FREE(errbuf);
- }
-
virErrorRestore(&orig_err);
return ret;
diff --git a/src/qemu/qemu_migration.h b/src/qemu/qemu_migration.h
index ed62fd4a91..039a926e69 100644
--- a/src/qemu/qemu_migration.h
+++ b/src/qemu/qemu_migration.h
@@ -236,8 +236,10 @@ qemuMigrationSrcIsAllowed(virDomainObj *vm,
int
qemuMigrationSrcToFile(virQEMUDriver *driver,
virDomainObj *vm,
- int fd,
+ int *fd,
virCommand *compressor,
+ qemuMigrationParams *migParams,
+ unsigned int flags,
virDomainAsyncJob asyncJob)
ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) G_GNUC_WARN_UNUSED_RESULT;
diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index b1c0c6a064..9a454a1d08 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -2237,6 +2237,42 @@ qemuMonitorMigrateToFd(qemuMonitor *mon,
}
+int
+qemuMonitorMigrateToFdSet(virDomainObj *vm,
+ unsigned int flags,
+ int *fd)
+{
+ qemuDomainObjPrivate *priv = vm->privateData;
+ qemuMonitor *mon = priv->mon;
+ off_t offset;
+ g_autoptr(qemuFDPass) fdPassMigrate = NULL;
+ unsigned int setId;
+ g_autofree char *uri = NULL;
+ int ret;
+
+ VIR_DEBUG("fd=%d flags=0x%x", *fd, flags);
+
+ QEMU_CHECK_MONITOR(mon);
+
+ if ((offset = lseek(*fd, 0, SEEK_CUR)) == -1) {
+ virReportSystemError(errno,
+ "%s", _("failed to seek on file
descriptor"));
+ return -1;
+ }
+
+ fdPassMigrate = qemuFDPassNew("migrate", priv);
+ qemuFDPassAddFD(fdPassMigrate, fd, "-buffered-fd");
+ if (qemuFDPassTransferMonitor(fdPassMigrate, mon) < 0)
+ return -1;
+
+ qemuFDPassGetId(fdPassMigrate, &setId);
+ uri = g_strdup_printf("file:/dev/fdset/%u,offset=%#lx", setId, offset);
+ ret = qemuMonitorJSONMigrate(mon, flags, uri);
+
+ return ret;
+}
+
+
int
qemuMonitorMigrateToHost(qemuMonitor *mon,
unsigned int flags,
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index 76c859a888..ebacdf110e 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -844,6 +844,10 @@ int qemuMonitorMigrateToFd(qemuMonitor *mon,
unsigned int flags,
int fd);
+int qemuMonitorMigrateToFdSet(virDomainObj *vm,
+ unsigned int flags,
+ int *fd);
+
int qemuMonitorMigrateToHost(qemuMonitor *mon,
unsigned int flags,
const char *protocol,
diff --git a/src/qemu/qemu_saveimage.c b/src/qemu/qemu_saveimage.c
index 6f2ce40124..98a1ad638d 100644
--- a/src/qemu/qemu_saveimage.c
+++ b/src/qemu/qemu_saveimage.c
@@ -96,6 +96,7 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC(virQEMUSaveData, virQEMUSaveDataFree);
*/
virQEMUSaveData *
virQEMUSaveDataNew(virQEMUDriver *driver,
+ virDomainObj *vm,
char *domXML,
qemuDomainSaveCookie *cookieObj,
bool running,
@@ -115,6 +116,19 @@ virQEMUSaveDataNew(virQEMUDriver *driver,
header = &data->header;
memcpy(header->magic, QEMU_SAVE_PARTIAL, sizeof(header->magic));
header->version = cfg->saveImageVersion;
+
+ /* Enable mapped-ram feature if available and save version >= 3 */
+ if (header->version >= QEMU_SAVE_VERSION &&
+ qemuMigrationCapsGet(vm, QEMU_MIGRATION_CAP_MAPPED_RAM)) {
+ if (compressed != QEMU_SAVE_FORMAT_RAW) {
+ virReportError(VIR_ERR_OPERATION_FAILED,
+ _("compression is not supported with save image version
%1$u"),
+ header->version);
+ goto error;
+ }
+ header->features |= QEMU_SAVE_FEATURE_MAPPED_RAM;
+ }
+
header->was_running = running ? 1 : 0;
header->compressed = compressed;
@@ -366,6 +380,7 @@ qemuSaveImageCreateFd(virQEMUDriver *driver,
virDomainObj *vm,
const char *path,
virFileWrapperFd *wrapperFd,
+ bool mappedRam,
bool *needUnlink,
unsigned int flags)
{
@@ -375,7 +390,7 @@ qemuSaveImageCreateFd(virQEMUDriver *driver,
int directFlag = 0;
unsigned int wrapperFlags = VIR_FILE_WRAPPER_NON_BLOCKING;
- if (flags & VIR_DOMAIN_SAVE_BYPASS_CACHE) {
+ if (!mappedRam && flags & VIR_DOMAIN_SAVE_BYPASS_CACHE) {
wrapperFlags |= VIR_FILE_WRAPPER_BYPASS_CACHE;
directFlag = virFileDirectFdFlag();
if (directFlag < 0) {
@@ -395,7 +410,7 @@ qemuSaveImageCreateFd(virQEMUDriver *driver,
if (qemuSecuritySetImageFDLabel(driver->securityManager, vm->def, fd) < 0)
return -1;
- if (!(wrapperFd = virFileWrapperFdNew(&fd, path, wrapperFlags)))
+ if (!mappedRam && !(wrapperFd = virFileWrapperFdNew(&fd, path,
wrapperFlags)))
return -1;
ret = fd;
@@ -414,6 +429,7 @@ qemuSaveImageCreate(virQEMUDriver *driver,
const char *path,
virQEMUSaveData *data,
virCommand *compressor,
+ qemuMigrationParams *saveParams,
unsigned int flags,
virDomainAsyncJob asyncJob)
{
@@ -422,9 +438,10 @@ qemuSaveImageCreate(virQEMUDriver *driver,
int ret = -1;
int fd = -1;
virFileWrapperFd *wrapperFd = NULL;
+ bool mappedRam = data->header.features & QEMU_SAVE_FEATURE_MAPPED_RAM;
/* Obtain the file handle. */
- fd = qemuSaveImageCreateFd(driver, vm, path, wrapperFd, &needUnlink, flags);
+ fd = qemuSaveImageCreateFd(driver, vm, path, wrapperFd, mappedRam, &needUnlink,
flags);
if (fd < 0)
goto cleanup;
@@ -433,7 +450,7 @@ qemuSaveImageCreate(virQEMUDriver *driver,
goto cleanup;
/* Perform the migration */
- if (qemuMigrationSrcToFile(driver, vm, fd, compressor, asyncJob) < 0)
+ if (qemuMigrationSrcToFile(driver, vm, &fd, compressor, saveParams, flags,
asyncJob) < 0)
goto cleanup;
/* Touch up file header to mark image complete. */
@@ -441,14 +458,18 @@ qemuSaveImageCreate(virQEMUDriver *driver,
/* Reopen the file to touch up the header, since we aren't set
* up to seek backwards on wrapperFd. The reopened fd will
* trigger a single page of file system cache pollution, but
- * that's acceptable. */
- if (VIR_CLOSE(fd) < 0) {
- virReportSystemError(errno, _("unable to close %1$s"), path);
- goto cleanup;
- }
+ * that's acceptable.
+ * If using mapped-ram, the fd was passed to qemu, so no need
+ * to close it. */
+ if (!mappedRam) {
+ if (VIR_CLOSE(fd) < 0) {
+ virReportSystemError(errno, _("unable to close %1$s"), path);
+ goto cleanup;
+ }
- if (qemuDomainFileWrapperFDClose(vm, wrapperFd) < 0)
- goto cleanup;
+ if (qemuDomainFileWrapperFDClose(vm, wrapperFd) < 0)
+ goto cleanup;
+ }
if ((fd = qemuDomainOpenFile(cfg, vm->def, path, O_WRONLY, NULL)) < 0 ||
virQEMUSaveDataFinish(data, &fd, path) < 0)
diff --git a/src/qemu/qemu_saveimage.h b/src/qemu/qemu_saveimage.h
index 3cee846f14..eb2835f11b 100644
--- a/src/qemu/qemu_saveimage.h
+++ b/src/qemu/qemu_saveimage.h
@@ -114,6 +114,7 @@ qemuSaveImageCreate(virQEMUDriver *driver,
const char *path,
virQEMUSaveData *data,
virCommand *compressor,
+ qemuMigrationParams *saveParams,
unsigned int flags,
virDomainAsyncJob asyncJob);
@@ -124,6 +125,7 @@ virQEMUSaveDataWrite(virQEMUSaveData *data,
virQEMUSaveData *
virQEMUSaveDataNew(virQEMUDriver *driver,
+ virDomainObj *vm,
char *domXML,
qemuDomainSaveCookie *cookieObj,
bool running,
diff --git a/src/qemu/qemu_snapshot.c b/src/qemu/qemu_snapshot.c
index 1d75208814..9833fb6206 100644
--- a/src/qemu/qemu_snapshot.c
+++ b/src/qemu/qemu_snapshot.c
@@ -1367,6 +1367,8 @@ qemuSnapshotCreateActiveExternal(virQEMUDriver *driver,
/* do the memory snapshot if necessary */
if (memory) {
+ g_autoptr(qemuMigrationParams) snap_params = NULL;
+
/* check if migration is possible */
if (!qemuMigrationSrcIsAllowed(vm, false, VIR_ASYNC_JOB_SNAPSHOT, 0))
goto cleanup;
@@ -1390,7 +1392,7 @@ qemuSnapshotCreateActiveExternal(virQEMUDriver *driver,
!(snapdef->cookie = (virObject *) qemuDomainSaveCookieNew(vm)))
goto cleanup;
- if (!(data = virQEMUSaveDataNew(driver, xml,
+ if (!(data = virQEMUSaveDataNew(driver, vm, xml,
(qemuDomainSaveCookie *) snapdef->cookie,
resume, compressed)))
goto cleanup;
@@ -1398,8 +1400,11 @@ qemuSnapshotCreateActiveExternal(virQEMUDriver *driver,
memory_existing = virFileExists(snapdef->memorysnapshotfile);
+ if (!(snap_params = qemuMigrationParamsNew()))
+ goto cleanup;
+
if ((ret = qemuSaveImageCreate(driver, vm, snapdef->memorysnapshotfile,
- data, compressor, 0,
+ data, compressor, snap_params, 0,
VIR_ASYNC_JOB_SNAPSHOT)) < 0)
goto cleanup;
--
2.35.3