Re: [pve-devel] [PATCH qemu-server] qemu options: add memory_allocator

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 13/03/2023 um 11:16 schrieb Alexandre Derumier:
> Add optional memory_allocator.
> 
> Default is glibc malloc, tcmalloc is available to improve performance
> of ceph librbd.

Looks ok besides some config/api schema details I'd like to see changed.

> 
> Signed-off-by: Alexandre Derumier <aderumier@odiso.com>
> ---
>  PVE/QemuServer.pm | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index 40be44d..8de6c82 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -723,6 +723,14 @@ EODESCR
>  	description => "List of host cores used to execute guest processes, for example: 0,5,8-11",
>  	optional => 1,
>      },
> +    memory_allocator => {

kebab-case for new properties please, but actually I'd like to have this nested
in a property string here, e.g.:

tuning => {
    optional => 1,
    type => 'string',
    format => { # <- probably in a $tuning_format variable
        allocator => {
             # ...
        },
    }
}

> +	optional => 1,
> +	type => 'string',
> +	enum => [ qw(glibc tcmalloc) ],

system tcmalloc

> +	default => 'glibc',
> +	description => "Configure qemu process memory allocator. tcmalloc improve performance of ceph librbd",

I'd change this to:

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,

you got "optional" set to true twice

> +    },
>  };
>  
>  my $cicustom_fmt = {
> @@ -5909,6 +5917,10 @@ sub vm_start_nolock {
>  
>      my $run_qemu = sub {
>  	PVE::Tools::run_fork sub {
> +
> +	    $ENV{LD_PRELOAD} = "/usr/lib/x86_64-linux-gnu/libtcmalloc.so.4"
> +		if $conf->{memory_allocator} && $conf->{memory_allocator} eq 'tcmalloc';
> +
>  	    PVE::Systemd::enter_systemd_scope($vmid, "Proxmox VE VM $vmid", %systemd_properties);
>  
>  	    my $tpmpid;