qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v3.1 00/31] NUMA series, and hostmem improvement


From: Hu Tao
Subject: Re: [Qemu-devel] [PATCH v3.1 00/31] NUMA series, and hostmem improvements
Date: Fri, 9 May 2014 16:29:49 +0800
User-agent: Mutt/1.5.21 (2010-09-15)

On Thu, May 08, 2014 at 04:51:56PM +0200, Paolo Bonzini wrote:
> Il 06/05/2014 11:27, Hu Tao ha scritto:
> > This series includes work on QOMifying the memory backends.
> > the idea is to delegate all properties of the memory backend to
> > a new QOM class hierarchy, in which the concrete classes
> > are hostmem-ram and hostmem-file.  The backend is passed to the
> > machine via "-numa node,memdev=foo" where "foo" is the id of the
> > backend object.
> 
> Hello,
> 
> I noticed now that if you have the host-nodes property set Linux
> requires you to set a policy other than "default" too.  If you don't,
> the mbind system call fails.
> 
> What about squashing something like this?
> 
> Paolo
> 
> diff --git a/backends/hostmem.c b/backends/hostmem.c
> index d3f8476..a0a3111 100644
> --- a/backends/hostmem.c
> +++ b/backends/hostmem.c
> @@ -299,12 +299,23 @@ host_memory_backend_memory_init(UserCreatable *uc, 
> Error **errp)
>  
>  #ifdef CONFIG_NUMA
>      unsigned long maxnode = find_last_bit(backend->host_nodes, MAX_NODES);
> +    unsigned policy = backend->policy;
> +
> +    /* Linux does not accept MPOL_DEFAULT with nonzero bitmap, but
> +     * "-object memory-ram,size=128M,hostnodes=0,policy=bind" is a
> +     * bit of a mouthful.  So if the host_nodes bitmap is nonzero,
> +     * pick the BIND policy.
> +     */
> +    if (find_first_bit(backend->host_nodes, MAX_NODES) != MAX_NODES &&
> +        policy == MPOL_DEFAULT) {
> +        policy = MPOL_BIND;
> +    }

This only changes the policy applied to memory. But info memdev still
shows the policy as 'default'(the 'default' here is interpreted as
'MPOL_DEFAULT', right?).

So this is related to how we deal with cases where 'policy' is not
specified in qemu:

1. if possible, the policy is set to MPOL_DEFAULT.
2. if host-nodes is not zero, the policy is set to MPOL_BIND.(set
   backend->policy too, other than just apply it)

Opinions?

>  
>      /* This is a workaround for a long standing bug in Linux'
>       * mbind implementation, which cuts off the last specified
>       * node.
>       */
> -    if (mbind(ptr, sz, backend->policy, backend->host_nodes, maxnode + 2, 
> 0)) {
> +    if (mbind(ptr, sz, policy, backend->host_nodes, maxnode + 2, 0)) {
>          error_setg_errno(errp, errno,
>                           "cannot bind memory to host NUMA nodes");



reply via email to

[Prev in Thread] Current Thread [Next in Thread]