[PATCH v1] pseries/hotplug-memory: hot-add: skip redundant LMB lookup

[Michael Ellerman]

Hi Scott,

Scott Cheloha <cheloha at linux.ibm.com> writes:
> During memory hot-add, dlpar_add_lmb() calls memory_add_physaddr_to_nid()
> to determine which node id (nid) to use when later calling __add_memory().
>
...
>
> Consider an LPAR with 126976 LMBs.  In one test, hot-adding 126000

Nice little machine you got there :P

> LMBs on an upatched kernel took ~3.5 hours while a patched kernel
> completed the same operation in ~2 hours:

...

> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 0ea976d1cac4..9cd572440175 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -595,6 +595,8 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
>  }
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>  
> +extern int of_drconf_to_nid_single(struct drmem_lmb *);
> +

This needs to go in a header.

It should probably go in arch/powerpc/include/asm/topology.h

cheers

>  static int dlpar_add_lmb(struct drmem_lmb *lmb)
>  {
>  	unsigned long block_sz;
> @@ -611,8 +613,10 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
>  
>  	block_sz = memory_block_size_bytes();
>  
> -	/* Find the node id for this address. */
> -	nid = memory_add_physaddr_to_nid(lmb->base_addr);
> +	/* Find the node id for this address.  Fake one if necessary. */
> +	nid = of_drconf_to_nid_single(lmb);
> +	if (nid < 0 || !node_possible(nid))
> +		nid = first_online_node;
>  
>  	/* Add the memory */
>  	rc = __add_memory(nid, lmb->base_addr, block_sz);
> -- 
> 2.24.1