linux-kernel - Re: [PATCH] memblock, numa: Binary search node id

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Date:	Fri, 16 Aug 2013 14:01:06 -0500
From:	Russ Anderson <rja@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Yinghai Lu <yinghai@...nel.org>, Tejun Heo <tj@...nel.org>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memblock, numa: Binary search node id

On Thu, Aug 15, 2013 at 01:43:48PM -0700, Andrew Morton wrote:
> On Wed, 14 Aug 2013 22:46:29 -0700 Yinghai Lu <yinghai@...nel.org> wrote:
> 
> > Current early_pfn_to_nid() on arch that support memblock go
> > over memblock.memory one by one, so will take too many try
> > near the end.
> > 
> > We can use existing memblock_search to find the node id for
> > given pfn, that could save some time on bigger system that
> > have many entries memblock.memory array.
> 
> Looks nice.  I wonder how much difference it makes.

Here are the timing differences for several machines.
In each case with the patch less time was spent in __early_pfn_to_nid().


                        3.11-rc5        with patch      difference (%)
                        --------        ----------      --------------
UV1: 256 nodes  9TB:     411.66          402.47         -9.19 (2.23%)
UV2: 255 nodes 16TB:    1141.02         1138.12         -2.90 (0.25%)
UV2:  64 nodes  2TB:     128.15          126.53         -1.62 (1.26%)
UV2:  32 nodes  2TB:     121.87          121.07         -0.80 (0.66%)
                        Time in seconds.

Acked-by: Russ Anderson <rja@....com>
 
> > ...
> >
> > --- linux-2.6.orig/include/linux/memblock.h
> > +++ linux-2.6/include/linux/memblock.h
> > @@ -60,6 +60,8 @@ int memblock_reserve(phys_addr_t base, p
> >  void memblock_trim_memory(phys_addr_t align);
> >  
> >  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> > +int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,
> > +			    unsigned long  *end_pfn);
> >  void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
> >  			  unsigned long *out_end_pfn, int *out_nid);
> >  
> > Index: linux-2.6/mm/memblock.c
> > ===================================================================
> > --- linux-2.6.orig/mm/memblock.c
> > +++ linux-2.6/mm/memblock.c
> > @@ -914,6 +914,24 @@ int __init_memblock memblock_is_memory(p
> >  	return memblock_search(&memblock.memory, addr) != -1;
> >  }
> >  
> > +#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> > +int __init_memblock memblock_search_pfn_nid(unsigned long pfn,
> > +			 unsigned long *start_pfn, unsigned long *end_pfn)
> > +{
> > +	struct memblock_type *type = &memblock.memory;
> > +	int mid = memblock_search(type, (phys_addr_t)pfn << PAGE_SHIFT);
> > +
> > +	if (mid == -1)
> > +		return -1;
> > +
> > +	*start_pfn = type->regions[mid].base >> PAGE_SHIFT;
> > +	*end_pfn = (type->regions[mid].base + type->regions[mid].size)
> > +			>> PAGE_SHIFT;
> > +
> > +	return type->regions[mid].nid;
> > +}
> > +#endif
> 
> This function will have no callers if
> CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID=y.  That's not too bad as the
> function is __init_memblock.  But this depends on
> CONFIG_ARCH_DISCARD_MEMBLOCK.  Messy :(
> 

-- 
Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          rja@....com
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