[pve-devel] [PATCH v2 qemu-server] qemu options: add tuning allocator

[Alexandre Derumier]

Add a new tuning option with allocator property.

Available values:
- Default is 'system', aka glibc malloc
- tcmalloc (improve performance ceph librbd)

Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
---
 PVE/QemuServer.pm | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 40be44d..761ab48 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -289,6 +289,19 @@ my $meta_info_fmt = {
     },
 };
 
+my $tuning_fmt = {
+    allocator => {
+	type => 'string',
+	enum => [ qw(system tcmalloc) ],
+	default => 'system',
+	description => "Override the memory allocator used in QEMU via LD_PRELOAD.",
+	verbose_description => "Override the memory allocator used in QEMU via LD_PRELOAD."
+	    ." Using tcmalloc might improve performance if ceph librbd is used."
+	    ." NOTE: you must install the libtcmalloc-minimal4 package first!",
+	optional => 1,
+    },
+};
+
 my $confdesc = {
     onboot => {
 	optional => 1,
@@ -723,6 +736,12 @@ EODESCR
 	description => "List of host cores used to execute guest processes, for example: 0,5,8-11",
 	optional => 1,
     },
+    tuning=> {
+	type => 'string',
+	format => $tuning_fmt,
+	description => "Tune some special features.",
+	optional => 1,
+    },
 };
 
 my $cicustom_fmt = {
@@ -2192,6 +2211,16 @@ sub parse_rng {
     return $res;
 }
 
+sub parse_tuning {
+    my ($value) = @_;
+
+    return if !$value;
+
+    my $res = eval { parse_property_string($tuning_fmt, $value) };
+    warn $@ if $@;
+    return $res;
+}
+
 sub parse_meta_info {
     my ($value) = @_;
 
@@ -5909,6 +5938,12 @@ sub vm_start_nolock {
 
     my $run_qemu = sub {
 	PVE::Tools::run_fork sub {
+
+	    my $tuning = $conf->{tuning} ? parse_tuning($conf->{tuning}) : undef;
+
+	    $ENV{LD_PRELOAD} = "/usr/lib/x86_64-linux-gnu/libtcmalloc.so.4"
+		if $tuning && $tuning->{allocator} eq 'tcmalloc';
+
 	    PVE::Systemd::enter_systemd_scope($vmid, "Proxmox VE VM $vmid", %systemd_properties);
 
 	    my $tpmpid;
-- 
2.30.2