--- /dev/null
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Fiona Ebner <f.ebner@proxmox.com>
+Date: Mon, 3 Oct 2022 15:52:04 +0200
+Subject: [PATCH] PVE Backup: allow passing max-workers performance setting
+
+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@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: