[pve-devel] [PATCH qemu 1/1] PVE Backup: allow passing max-workers performance setting

[Fiona Ebner]

For query-proxmox-support, add an indication that it's possible to use
the setting.

For now, the other two BackupPerf settings are not exposed:

* use-copy-range: would need to be implemented by the backup-dump
block driver first, and in fact, the default for backup was changed,
because it wasn't as fast for backup in QEMU, see commit
6a30f663d4c0b3c45a544d541e0c4e214b2473a1.

* max-chunk: enforced to be at least the backup cluster size, which is
4 MiB for PBS and otherwise maximum of source and target cluster size.
And block-copy has a maximum buffer size of 1 MiB, so setting a larger
max-chunk doesn't even have an effect. To make the setting sensibly
usable the check would need to be removed and optionally the
block-copy max buffer size would need to be bumped. I tried doing just
that, and tested different source/target combinations with different
max-chunk settings, but there were no noticable improvements over the
default "unlimited" (resulting in 1 MiB for block-copy).

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
 block/monitor/block-hmp-cmds.c |  4 +++-
 pve-backup.c                   | 18 +++++++++++++-----
 qapi/block-core.json           |  9 +++++++--
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index 0502f42be6..cc231ec3f2 100644
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -1049,7 +1049,9 @@ void coroutine_fn hmp_backup(Monitor *mon, const QDict *qdict)
         false, false, // PBS encrypt
         true, dir ? BACKUP_FORMAT_DIR : BACKUP_FORMAT_VMA,
         false, NULL, false, NULL, !!devlist,
-        devlist, qdict_haskey(qdict, "speed"), speed, &error);
+        devlist, qdict_haskey(qdict, "speed"), speed,
+        false, 0, // BackupPerf max-workers
+        &error);
 
     hmp_handle_error(mon, error);
 }
diff --git a/pve-backup.c b/pve-backup.c
index 2e22030eec..e9aa7e0f49 100644
--- a/pve-backup.c
+++ b/pve-backup.c
@@ -55,6 +55,7 @@ static struct PVEBackupState {
         bool starting;
     } stat;
     int64_t speed;
+    BackupPerf perf;
     VmaWriter *vmaw;
     ProxmoxBackupHandle *pbs;
     GList *di_list;
@@ -492,8 +493,6 @@ static void create_backup_jobs_bh(void *opaque) {
     }
     backup_state.txn = job_txn_new_seq();
 
-    BackupPerf perf = { .max_workers = 16 };
-
     /* create and start all jobs (paused state) */
     GList *l =  backup_state.di_list;
     while (l) {
@@ -513,8 +512,9 @@ static void create_backup_jobs_bh(void *opaque) {
 
         BlockJob *job = backup_job_create(
             NULL, di->bs, di->target, backup_state.speed, sync_mode, di->bitmap,
-            bitmap_mode, false, NULL, &perf, BLOCKDEV_ON_ERROR_REPORT, BLOCKDEV_ON_ERROR_REPORT,
-            JOB_DEFAULT, pvebackup_complete_cb, di, backup_state.txn, &local_err);
+            bitmap_mode, false, NULL, &backup_state.perf, BLOCKDEV_ON_ERROR_REPORT,
+            BLOCKDEV_ON_ERROR_REPORT, JOB_DEFAULT, pvebackup_complete_cb, di, backup_state.txn,
+            &local_err);
 
         di->job = job;
         if (job) {
@@ -584,7 +584,9 @@ UuidInfo coroutine_fn *qmp_backup(
     bool has_config_file, const char *config_file,
     bool has_firewall_file, const char *firewall_file,
     bool has_devlist, const char *devlist,
-    bool has_speed, int64_t speed, Error **errp)
+    bool has_speed, int64_t speed,
+    bool has_max_workers, int64_t max_workers,
+    Error **errp)
 {
     assert(qemu_in_coroutine());
 
@@ -914,6 +916,11 @@ UuidInfo coroutine_fn *qmp_backup(
 
     backup_state.speed = (has_speed && speed > 0) ? speed : 0;
 
+    backup_state.perf = (BackupPerf){ .max_workers = 16 };
+    if (has_max_workers) {
+        backup_state.perf.max_workers = max_workers;
+    }
+
     backup_state.vmaw = vmaw;
     backup_state.pbs = pbs;
 
@@ -1089,5 +1096,6 @@ ProxmoxSupportStatus *qmp_query_proxmox_support(Error **errp)
     ret->pbs_dirty_bitmap_migration = true;
     ret->query_bitmap_info = true;
     ret->pbs_masterkey = true;
+    ret->backup_max_workers = true;
     return ret;
 }
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 89875f309c..43281aca79 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -833,6 +833,8 @@
 #
 # @encrypt: use encryption ((optional for format 'pbs', defaults to true if there is a keyfile)
 #
+# @max-workers: see @BackupPerf for details. Default 16.
+#
 # Returns: the uuid of the backup job
 #
 ##
@@ -851,7 +853,9 @@
                                     '*format': 'BackupFormat',
                                     '*config-file': 'str',
                                     '*firewall-file': 'str',
-                                    '*devlist': 'str', '*speed': 'int' },
+                                    '*devlist': 'str',
+                                    '*speed': 'int',
+                                    '*max-workers': 'int' },
   'returns': 'UuidInfo', 'coroutine': true }
 
 ##
@@ -906,7 +910,8 @@
             'pbs-dirty-bitmap-savevm': 'bool',
             'pbs-dirty-bitmap-migration': 'bool',
             'pbs-masterkey': 'bool',
-            'pbs-library-version': 'str' } }
+            'pbs-library-version': 'str',
+            'backup-max-workers': 'bool' } }
 
 ##
 # @query-proxmox-support:
-- 
2.30.2