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backup: trim heap after finishing

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Reported in the community forum [0]. By default, there can be large
amounts of memory left assigned to the QEMU process after backup.
Likely because of fragmentation, it's necessary to explicitly call
malloc_trim() to tell glibc that it shouldn't keep all that memory
resident for the process.

QEMU itself already does a malloc_trim() in the RCU thread, but that
code path might not be reached (or not for a long time) under usual
operation. The value of 4 MiB for the argument was also copied from
there.

Example with the following configuration:
> agent: 1
> boot: order=scsi0
> cores: 4
> cpu: x86-64-v2-AES
> ide2: none,media=cdrom
> memory: 1024
> name: backup-mem
> net0: virtio=DA:58:18:26:59:9F,bridge=vmbr0,firewall=1
> numa: 0
> ostype: l26
> scsi0: rbd:base-107-disk-0/vm-106-disk-1,size=4302M
> scsihw: virtio-scsi-pci
> smbios1: uuid=b2d4511e-8d01-44f1-afd6-9581b30c24a6
> sockets: 2
> startup: order=2
> virtio0: lvmthin:vm-106-disk-1,iothread=1,size=1G
> virtio1: lvmthin:vm-106-disk-2,iothread=1,size=1G
> virtio2: lvmthin:vm-106-disk-3,iothread=1,size=1G
> vmgenid: 0a1d8751-5e02-449d-977e-c0160e900231

Before the change:

> root@pve8a1 ~ # grep VmRSS /proc/$(cat /var/run/qemu-server/106.pid)/status
> VmRSS:	  370948 kB
> root@pve8a1 ~ # vzdump 106 --storage pbs
> (...)
> INFO: Backup job finished successfully
> root@pve8a1 ~ # grep VmRSS /proc/$(cat /var/run/qemu-server/106.pid)/status
> VmRSS:	 2114964 kB

After the change:

> root@pve8a1 ~ # grep VmRSS /proc/$(cat /var/run/qemu-server/106.pid)/status
> VmRSS:	  398788 kB
> root@pve8a1 ~ # vzdump 106 --storage pbs
> (...)
> INFO: Backup job finished successfully
> root@pve8a1 ~ # grep VmRSS /proc/$(cat /var/run/qemu-server/106.pid)/status
> VmRSS:	  424356 kB

[0]: https://forum.proxmox.com/threads/131339/

Co-diagnosed-by: Friedrich Weber <f.weber@proxmox.com>
Co-diagnosed-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Acked-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
This commit is contained in:
Fiona Ebner 2023-08-14 10:53:19 +02:00
parent c36e3f9d17
commit 5f9cb29c3a
2 changed files with 20 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
debian/patches/pve/0030-PVE-Backup-Proxmox-backup-patches-for-QEMU.patch vendored
View File

@ -79,7 +79,8 @@ Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
adapt for new job lock mechanism replacing AioContext locks adapt for new job lock mechanism replacing AioContext locks
adapt to QAPI changes adapt to QAPI changes
improve canceling improve canceling
allow passing max-workers setting] allow passing max-workers setting
use malloc_trim after backup]
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
--- ---
block/meson.build | 5 + block/meson.build | 5 +
@ -92,11 +93,11 @@ Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
monitor/hmp-cmds.c | 72 +++ monitor/hmp-cmds.c | 72 +++
proxmox-backup-client.c | 146 +++++ proxmox-backup-client.c | 146 +++++
proxmox-backup-client.h | 60 ++ proxmox-backup-client.h | 60 ++
pve-backup.c | 1097 ++++++++++++++++++++++++++++++++ pve-backup.c | 1109 ++++++++++++++++++++++++++++++++
qapi/block-core.json | 226 +++++++ qapi/block-core.json | 226 +++++++
qapi/common.json | 13 + qapi/common.json | 13 +
qapi/machine.json | 15 +- qapi/machine.json | 15 +-
14 files changed, 1711 insertions(+), 13 deletions(-) 14 files changed, 1723 insertions(+), 13 deletions(-)
create mode 100644 proxmox-backup-client.c create mode 100644 proxmox-backup-client.c
create mode 100644 proxmox-backup-client.h create mode 100644 proxmox-backup-client.h
create mode 100644 pve-backup.c create mode 100644 pve-backup.c
@ -587,10 +588,10 @@ index 0000000000..8cbf645b2c
+#endif /* PROXMOX_BACKUP_CLIENT_H */ +#endif /* PROXMOX_BACKUP_CLIENT_H */
diff --git a/pve-backup.c b/pve-backup.c diff --git a/pve-backup.c b/pve-backup.c
new file mode 100644 new file mode 100644
index 0000000000..dd72ee0ed6 index 0000000000..10ca8a0b1d
--- /dev/null --- /dev/null
+++ b/pve-backup.c +++ b/pve-backup.c
@@ -0,0 +1,1097 @@ @@ -0,0 +1,1109 @@
+#include "proxmox-backup-client.h" +#include "proxmox-backup-client.h"
+#include "vma.h" +#include "vma.h"
+ +
@ -605,6 +606,10 @@ index 0000000000..dd72ee0ed6
+#include "qapi/qmp/qerror.h" +#include "qapi/qmp/qerror.h"
+#include "qemu/cutils.h" +#include "qemu/cutils.h"
+ +
+#if defined(CONFIG_MALLOC_TRIM)
+#include <malloc.h>
+#endif
+
+#include <proxmox-backup-qemu.h> +#include <proxmox-backup-qemu.h>
+ +
+/* PVE backup state and related function */ +/* PVE backup state and related function */
@ -869,6 +874,14 @@ index 0000000000..dd72ee0ed6
+ backup_state.stat.end_time = time(NULL); + backup_state.stat.end_time = time(NULL);
+ backup_state.stat.finishing = false; + backup_state.stat.finishing = false;
+ qemu_mutex_unlock(&backup_state.stat.lock); + qemu_mutex_unlock(&backup_state.stat.lock);
+
+#if defined(CONFIG_MALLOC_TRIM)
+ /*
+ * Try to reclaim memory for buffers (and, in case of PBS, Rust futures), etc.
+ * Won't happen by default if there is fragmentation.
+ */
+ malloc_trim(4 * 1024 * 1024);
+#endif
+} +}
+ +
+static void coroutine_fn pvebackup_co_complete_stream(void *opaque) +static void coroutine_fn pvebackup_co_complete_stream(void *opaque)

4
debian/patches/pve/0034-PVE-Migrate-dirty-bitmap-state-via-savevm.patch vendored
View File

@ -175,10 +175,10 @@ index 0000000000..887e998b9e
+ NULL); + NULL);
+} +}
diff --git a/pve-backup.c b/pve-backup.c diff --git a/pve-backup.c b/pve-backup.c
index dd72ee0ed6..cb5312fff3 100644 index 10ca8a0b1d..0a5ce2cab8 100644
--- a/pve-backup.c --- a/pve-backup.c
+++ b/pve-backup.c +++ b/pve-backup.c
@@ -1090,6 +1090,7 @@ ProxmoxSupportStatus *qmp_query_proxmox_support(Error **errp) @@ -1102,6 +1102,7 @@ ProxmoxSupportStatus *qmp_query_proxmox_support(Error **errp)
ret->pbs_library_version = g_strdup(proxmox_backup_qemu_version()); ret->pbs_library_version = g_strdup(proxmox_backup_qemu_version());
ret->pbs_dirty_bitmap = true; ret->pbs_dirty_bitmap = true;
ret->pbs_dirty_bitmap_savevm = true; ret->pbs_dirty_bitmap_savevm = true;