[dpdk-dev] [PATCH v6 12/19] malloc: fix the issue of SOCKET_ID_ANY

[Neil Horman]

On Sun, Feb 15, 2015 at 12:43:03AM +0000, Liang, Cunming wrote:
> Hi,
> 
> > -----Original Message-----
> > From: Neil Horman [mailto:nhorman at tuxdriver.com]
> > Sent: Saturday, February 14, 2015 1:57 AM
> > To: Liang, Cunming
> > Cc: dev at dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH v6 12/19] malloc: fix the issue of SOCKET_ID_ANY
> > 
> > On Fri, Feb 13, 2015 at 09:38:14AM +0800, Cunming Liang wrote:
> > > Add check for rte_socket_id(), avoid get unexpected return like (-1).
> > >
> > > Signed-off-by: Cunming Liang <cunming.liang at intel.com>
> > > ---
> > >  lib/librte_malloc/malloc_heap.h | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/lib/librte_malloc/malloc_heap.h b/lib/librte_malloc/malloc_heap.h
> > > index b4aec45..a47136d 100644
> > > --- a/lib/librte_malloc/malloc_heap.h
> > > +++ b/lib/librte_malloc/malloc_heap.h
> > > @@ -44,7 +44,12 @@ extern "C" {
> > >  static inline unsigned
> > >  malloc_get_numa_socket(void)
> > >  {
> > > -	return rte_socket_id();
> > > +	unsigned socket_id = rte_socket_id();
> > > +
> > > +	if (socket_id == (unsigned)SOCKET_ID_ANY)
> > > +		return 0;
> > > +
> > > +	return socket_id;
> > Why is -1 unexpected?  Isn't it reasonable to assume that some memory is
> > equidistant from all cpu numa nodes?
> [LCM] One piece of memory will be whole allocated from one specific NUMA node. But won't be like some part from one and the other part from another.
> If no specific NUMA node assigned(SOCKET_ID_ANY/-1), it firstly asks for the current NUMA node where current core belongs to.
> 'malloc_get_numa_socket()' is called on that time. When the time 1:1 thread/core mapping is assumed and the default value is 0, it always will return a none (-1) value.
> Now rte_socket_id() may return -1 in the case the pthread runs on multi-cores which are not belongs to one NUMA node, or in the case _socket_id is not yet assigned and the default value is (-1). So if current _socket_id is -1, then just pick up the first node as the candidate. Probably I shall add more comments for this.
> > 
Ok, but doesn't that provide an abnormal bias for node 0?  I was thinking it
might be better to be honest with the application so that it can choose a node
according to its own policy.

Neil

> > Neil
> > 
> > >  }
> > >
> > >  void *
> > > --
> > > 1.8.1.4
> > >
> > >
>