On 12/07/2016 16:34, Peter Lieven wrote:
> Am 11.07.2016 um 12:37 schrieb Paolo Bonzini:
>>
>> 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?
>
> Of course, but please see my other comment. We still should consider mmap for
> this cause we have close to 500 Physmaps about 70KB each which
> are all allocted at the same time - I think due to RCU.
That I think is not material for 2.7, and also I want to take a look at
creating nodes lazily.
Paolo
