[pve-devel] [PATCH qemu-server 1/1] migrate cache-size : power of 2

[Alexandre DERUMIER]

>>that is wrong though unless $memory is already a power of 2, which is 
>>not guarantueed at all. we need to round to the nearest power of 2 (and 
>>then we can also keep the 10% ;)) 

yes, you are right. I just sent a new patch.

----- Mail original -----
De: "Fabian Grünbichler" <f.gruenbichler at proxmox.com>
À: "pve-devel" <pve-devel at pve.proxmox.com>
Envoyé: Lundi 12 Février 2018 09:03:42
Objet: Re: [pve-devel] [PATCH qemu-server 1/1] migrate cache-size : power of 2

On Fri, Feb 09, 2018 at 07:29:35PM +0100, Alexandre Derumier wrote: 
> qemu 2.11 need a power of 2 cache size. 
> 
> " 
> Parameter 'xbzrle_cache_size' expects is invalid, 
> it should be bigger than target page size and a power of two 
> " 
> 
> Divide the memory size by 8 instead 10 
> --- 
> PVE/QemuMigrate.pm | 4 ++-- 
> 1 file changed, 2 insertions(+), 2 deletions(-) 
> 
> diff --git a/PVE/QemuMigrate.pm b/PVE/QemuMigrate.pm 
> index 937a855..a61e34b 100644 
> --- a/PVE/QemuMigrate.pm 
> +++ b/PVE/QemuMigrate.pm 
> @@ -688,9 +688,9 @@ sub phase2 { 
> }; 
> warn $@ if $@; 
> 
> - # set cachesize to 10% of the total memory 
> + # set cachesize to 12,5% of the total memory 
> my $memory = $conf->{memory} || $defaults->{memory}; 
> - my $cachesize = int($memory * 1048576 / 10); 
> + my $cachesize = int($memory * 1048576 / 8); 

that is wrong though unless $memory is already a power of 2, which is 
not guarantueed at all. we need to round to the nearest power of 2 (and 
then we can also keep the 10% ;)) 

> $self->log('info', "set cachesize: $cachesize"); 
> eval { 
> PVE::QemuServer::vm_mon_cmd_nocheck($vmid, "migrate-set-cache-size", value => int($cachesize)); 
> -- 
> 2.11.0 
> 
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