[pve-devel] [PATCH v4 qemu-server 12/16] memory: use 64 slots && static dimm size when max is defined

[Alexandre Derumier]

default kernel vhost config only support 64 slots by default,
for performance since 2015.

Original memory hotplug code was done before, using qemu
max supported 255 slots.

To reach max mem (4TB), we used incremental dimm size.

Instead of dynamic memory size, use 1 static dimm size, compute
from max memory/64.

We also force a static memory to 4GB, as memory under 4G don't
works fine with unplug

Fix:
https://bugzilla.proxmox.com/show_bug.cgi?id=3446
https://bugzilla.proxmox.com/show_bug.cgi?id=1426
Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
---
 PVE/QemuServer/Memory.pm | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/PVE/QemuServer/Memory.pm b/PVE/QemuServer/Memory.pm
index cf1ddb9..1b1c99d 100644
--- a/PVE/QemuServer/Memory.pm
+++ b/PVE/QemuServer/Memory.pm
@@ -19,6 +19,7 @@ get_host_max_mem
 );
 
 my $MAX_NUMA = 8;
+my $MAX_SLOTS = 64;
 
 our $memory_fmt = {
     current => {
@@ -71,7 +72,13 @@ my sub get_static_mem {
     my $static_memory = 0;
     my $memory = parse_memory($conf->{memory});
 
-    if ($hotplug) {
+    if ($memory->{max}) {
+	my $dimm_size = $memory->{max} / $MAX_SLOTS;
+	#static mem can't be lower than 4G and lower than 1 dimmsize by socket
+	$static_memory = $dimm_size * $sockets;
+	$static_memory = 4096 if $static_memory < 4096;
+    } elsif ($hotplug) {
+	#legacy
 	$static_memory = 1024;
 	$static_memory = $static_memory * $sockets if ($conf->{hugepages} && $conf->{hugepages} == 1024);
     } else {
@@ -194,7 +201,10 @@ sub foreach_dimm{
     my $current_size = $static_memory;
     my $dimm_size = 0;
 
-    if($conf->{hugepages} && $conf->{hugepages} == 1024) {
+    my $confmem = parse_memory($conf->{memory});
+    if ($confmem->{max}) {
+	$dimm_size = $confmem->{max} / $MAX_SLOTS;
+    } elsif($conf->{hugepages} && $conf->{hugepages} == 1024) {
 	$dimm_size = 1024;
     } else {
 	$dimm_size = 512;
@@ -213,7 +223,7 @@ sub foreach_dimm{
 	    &$func($conf, $vmid, $name, $dimm_size, $numanode, $current_size, $memory);
 	    return  $current_size if $current_size >= $memory;
 	}
-	$dimm_size *= 2;
+	$dimm_size *= 2 if !$confmem->{max};
     }
 }
 
@@ -368,7 +378,9 @@ sub config {
 	}
 
 	die "minimum memory must be ${static_memory}MB\n" if($memory < $static_memory);
-	push @$cmd, '-m', "size=${static_memory},slots=255,maxmem=${MAX_MEM}M";
+	my $confmem = parse_memory($conf->{memory});
+	my $slots = $confmem->{max} ? $MAX_SLOTS : 255;
+	push @$cmd, '-m', "size=${static_memory},slots=$slots,maxmem=${MAX_MEM}M";
 
     } else {
 
-- 
2.30.2