On Fri, Aug 21, 2020 at 10:33:10AM +0200, Laurent Dufour wrote:
> Le 11/08/2020 à 03:51, Scott Cheloha a écrit :
> >
> > [...]
> >
> > @@ -631,7 +638,7 @@ static int dlpar_memory_remove_by_ic(u32
> > lmbs_to_remove, u32 drc_index)
> > static int dlpar_add_lmb(struct drmem_lmb *lmb)
> > {
> > unsigned long block_sz;
> > - int rc;
> > + int nid, rc;
> >
> > if (lmb->flags & DRCONF_MEM_ASSIGNED)
> > return -EINVAL;
> > @@ -642,11 +649,13 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
> > return rc;
> > }
> >
> > - lmb_set_nid(lmb);
> > block_sz = memory_block_size_bytes();
> >
> > + /* Find the node id for this address. */
> > + nid = memory_add_physaddr_to_nid(lmb->base_addr);
>
> I think we could be more efficient here.
> Here is the call stack behind memory_add_physaddr_to_nid():
>
> memory_add_physaddr_to_nid(lmb->base_addr)
> hot_add_scn_to_nid()
> if (of_find_node_by_path("/ibm,dynamic-reconfiguration-memory")) ==
> true*
> then
> hot_add_drconf_scn_to_nid()
> for_each_drmem_lmb() to find the LMB based on lmb->base_addr
> of_drconf_to_nid_single(found LMB)
> use lmb->aa_index to get the nid.
>
> * that test is necessarily true when called from dlpar_add_lmb()
> otherwise the call to update_lmb_associativity_index() would have
> failed earlier.
>
> Basically, we have a LMB and we later walk all the LMBs to find that lmb
> again. In the case of dlpar_add_lmb(), it would be more efficient to
> directly call of_drconf_to_nid_single(). That function is not exported
> from arch/powerpc/mm/numa.c but it may be good to export it through that
> patch.
I've posted a patch for this:
https://lore.kernel.org/linuxppc-dev/20200910175637.2865160-1-chel...@linux.ibm.com/T/#u
The speedup is nice, especially for LMBs at the end of the array.
