(2014/01/15 3:24), Nathan Zimmer wrote:
> We don't need to do register_memory_resource() since it has its own lock and
> doesn't make any callbacks.
>
> Also register_memory_resource return NULL on failure so we don't have anything
> to cleanup at this point.
>
>
> The reason for this rfc is I was doing some experiments with hotplugging of
> memory on some of our larger systems. While it seems to work, it can be quite
> slow. With some preliminary digging I found that lock_memory_hotplug is
> clearly ripe for breakup.
>
> It could be broken up per nid or something but it also covers the
> online_page_callback. The online_page_callback shouldn't be very hard to break
> out.
>
> Also there is the issue of various structures(wmarks come to mind) that are
> only updated under the lock_memory_hotplug that would need to be dealt with.
>
>
> cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> cc: Tang Chen <tangchen@xxxxxxxxxxxxxx>
> cc: Wen Congyang <wency@xxxxxxxxxxxxxx>
> cc: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
> cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
> cc: Hedi <hedi@xxxxxxx>
> cc: Mike Travis <travis@xxxxxxx>
> cc: linux-mm@xxxxxxxxx
> cc: linux-kernel@xxxxxxxxxxxxxxx
>
>
> ---
The patch seems good to me.
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Thanks,
Yasuaki Ishimatsu
> mm/memory_hotplug.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 1ad92b4..62a0cd1 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1097,17 +1097,18 @@ int __ref add_memory(int nid, u64 start, u64 size)
> struct resource *res;
> int ret;
>
> - lock_memory_hotplug();
> -
> res = register_memory_resource(start, size);
> ret = -EEXIST;
> if (!res)
> - goto out;
> + return ret;
>
> { /* Stupid hack to suppress address-never-null warning */
> void *p = NODE_DATA(nid);
> new_pgdat = !p;
> }
> +
> + lock_memory_hotplug();
> +
> new_node = !node_online(nid);
> if (new_node) {
> pgdat = hotadd_new_pgdat(nid, start);
>
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