On Tue, May 06, 2014 at 05:27:46PM +0800, Hu Tao wrote:
[...]
> @@ -203,6 +296,20 @@ host_memory_backend_memory_init(UserCreatable *uc, Error
> **errp)
> if (backend->prealloc) {
> os_mem_prealloc(memory_region_get_fd(&backend->mr), ptr, sz);
> }
> +
> +#ifdef CONFIG_NUMA
> + unsigned long maxnode = find_last_bit(backend->host_nodes, MAX_NODES);
> +
> + /* This is a workaround for a long standing bug in Linux'
> + * mbind implementation, which cuts off the last specified
> + * node.
> + */
What if the bug is fixed? mbind() documentation says "nodemask points to
a bit mask of nodes containing up to maxnode bits", so we must ensure
backend->host_nodes has the one extra bit.
Also, if no bit is set, we can pass nodemask=NULL or maxnode=0 as
argument.
We could address both issues, and do this:
struct HostMemoryBackend { [...]
DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
[...]
lastbit = find_last_bit(backend->host_nodes, MAX_NODES);
/* lastbit == MAX_NODES means maxnode=0 */
maxnode = (lastbit + 1) % (MAX_NODES + 1);
/* We can have up to MAX_NODES nodes, but we need to pass maxnode+1
* as argument to mbind() due to an old Linux bug (feature?) which
* cuts off the last specified node. This means backend->host_nodes
* must have MAX_NODES+1 bits available.
*/
assert(sizeof(backend->host_nodes) >= BITS_TO_LONGS(MAX_NODES + 1) *
sizeof(unsigned long));
assert(maxnode <= MAX_NODES);
mbind(ptr, sz, policy, maxnode ? backend->host_nodes : NULL, maxnode + 1,
flags);
(I am starting to wonder if it was worth dropping the libnuma
requirement and implementing our own mbind()-calling code.)
> + if (mbind(ptr, sz, backend->policy, backend->host_nodes, maxnode + 2,
> 0)) {
> + error_setg_errno(errp, errno,
> + "cannot bind memory to host NUMA nodes");
Don't we want to set flags to MPOL_MF_STRICT here? I believe we
shouldn't have any pages preallocated at this point, but in case we do,
I would expect them to be moved instead of ignoring the policy set by
the user.
> + return;
> + }
> +#endif
> }
>
> MemoryRegion *
> diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
> index 819b72d..4e96298 100644
> --- a/include/sysemu/hostmem.h
> +++ b/include/sysemu/hostmem.h
> @@ -12,8 +12,10 @@
> #ifndef QEMU_HOSTMEM_H
> #define QEMU_HOSTMEM_H
>
> +#include "sysemu/sysemu.h" /* for MAX_NODES */
> #include "qom/object.h"
> #include "exec/memory.h"
> +#include "qemu/bitmap.h"
>
> #define TYPE_MEMORY_BACKEND "memory"
> #define MEMORY_BACKEND(obj) \
> @@ -52,6 +54,8 @@ struct HostMemoryBackend {
> uint64_t size;
> bool merge, dump;
> bool prealloc, force_prealloc;
> + DECLARE_BITMAP(host_nodes, MAX_NODES);
> + HostMemPolicy policy;
>
> MemoryRegion mr;
> };
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 5dd30eb..bea3476 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -4732,3 +4732,23 @@
> '*cpus': ['uint16'],
> '*mem': 'size',
> '*memdev': 'str' }}
> +
> +##
> +# @HostMemPolicy
> +#
> +# Host memory policy types
> +#
> +# @default: restore default policy, remove any nondefault policy
> +#
> +# @preferred: set the preferred host nodes for allocation
> +#
> +# @bind: a strict policy that restricts memory allocation to the
> +# host nodes specified
> +#
> +# @interleave: memory allocations are interleaved across the set
> +# of host nodes specified
> +#
> +# Since 2.1
> +##
> +{ 'enum': 'HostMemPolicy',
> + 'data': [ 'default', 'preferred', 'bind', 'interleave' ] }
> --
> 1.8.5.2.229.g4448466
>
>
--
Eduardo
