On 11/07/2016 11:31, Peter Lieven wrote:
> Am 28.06.2016 um 12:43 schrieb Paolo Bonzini:
>>
>> On 28/06/2016 11:01, Peter Lieven wrote:
>>> this was causing serious framentation in conjunction with the
>>> subpages since RCU was introduced. The node space was allocated
>>> at approx 32kB then reallocted to approx 75kB and this a few hundred
>>> times at startup. And thanks to RCU the freeing was delayed.
>>>
>>> Signed-off-by: Peter Lieven <p...@kamp.de>
>> The size of the node from the previous as->dispatch could be used as a
>> hint for the new one perhaps, avoiding the reallocation?
>
> This here seems also to work:
>
> diff --git a/exec.c b/exec.c
> index 0122ef7..2691c0a 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -187,10 +187,12 @@ struct CPUAddressSpace {
>
> static void phys_map_node_reserve(PhysPageMap *map, unsigned nodes)
> {
> + static unsigned alloc_hint = 16;
> if (map->nodes_nb + nodes > map->nodes_nb_alloc) {
> - map->nodes_nb_alloc = MAX(map->nodes_nb_alloc * 2, 16);
> + map->nodes_nb_alloc = MAX(map->nodes_nb_alloc, alloc_hint);
> map->nodes_nb_alloc = MAX(map->nodes_nb_alloc, map->nodes_nb +
> nodes);
> map->nodes = g_renew(Node, map->nodes, map->nodes_nb_alloc);
> + alloc_hint = map->nodes_nb_alloc;
> }
> }
>
>
> Question is still, mmap for this?
Nice! Can you submit a patch for this?
Paolo
