Date:	Mon, 06 Jul 2015 09:42:34 -0700 (PDT)
From:	Yasuaki Ishimatsu <yasu.isimatu@...il.com>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	Xishi Qiu <qiuxishi@...wei.com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <hpa@...or.com>, <akpm@...ux-foundation.org>,
	<tj@...nel.org>, <dyoung@...hat.com>,
	<isimatu.yasuaki@...fujitsu.com>, <lcapitulino@...hat.com>,
	<will.deacon@....com>, <tony.luck@...el.com>,
	<vladimir.murzin@....com>, <fabf@...net.be>,
	<kuleshovmail@...il.com>, <bhe@...hat.com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	Yasuaki Ishimatsu <yasu.isimatu@...il.com>
Subject: Re: [PATCH 1/1] mem-hotplug: Handle node hole when initializing
 numa_meminfo.


On Fri, 3 Jul 2015 09:26:05 +0800
Tang Chen <tangchen@...fujitsu.com> wrote:

> 
> On 07/02/2015 11:02 PM, Yasuaki Ishimatsu wrote:
> > Hi Tang,
> >
> >> On my box, if I run lscpu, the output looks like this:
> >>
> >> NUMA node0 CPU(s):     0-14,128-142
> >> NUMA node1 CPU(s):     15-29,143-157
> >> NUMA node2 CPU(s):
> >> NUMA node3 CPU(s):
> >> NUMA node4 CPU(s):     62-76,190-204
> >> NUMA node5 CPU(s):     78-92,206-220
> >>
> >> Node 2 and 3 are not exist, but they are online.
> > According your description of patch, node 4 and 5 are mistakenly
> 
> Not node 4 and 5, it is node 2 and 3 which are mistakenly set online.

Please add the results of lscpu before/after applyinig the patch into
description of your patch.

Feel free to add my 
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>

Thanks,
Yasuaki Ishimatsu

> > set to online. Why does lscpu show the above result?
> 
> Well, actually not only lscpu gives the strange result, under 
> /sys/device/system/node,
> interfaces for node 2 and 3 are also created.
> 
> I haven't read lscpu code, so I'm not sure how lscpu handles nodes. But 
> obviously,
> node 2 and 3 are set online, which is incorrect.
> 
> For now, I only found that in numa_cleanup_meminfo(), memory above 
> max_pfn is removed,
> but holes between nodes are not removed.
> 
> I think libraries are not able to handle this problem since nodes are 
> set online in kernel.
> Seeing from user space, there is no hole.
> 
> Thanks.
> 
> >
> > Thanks,
> > Yasuaki Ishimatsu
> >
> > On Wed, 1 Jul 2015 15:55:30 +0800
> > Tang Chen <tangchen@...fujitsu.com> wrote:
> >
> >> On 07/01/2015 02:25 PM, Xishi Qiu wrote:
> >>> On 2015/7/1 11:16, Tang Chen wrote:
> >>>
> >>>> When parsing SRAT, all memory ranges are added into numa_meminfo.
> >>>> In numa_init(), before entering numa_cleanup_meminfo(), all possible
> >>>> memory ranges are in numa_meminfo. And numa_cleanup_meminfo() removes
> >>>> all ranges over max_pfn or empty.
> >>>>
> >>>> But, this only works if the nodes are continuous. Let's have a look
> >>>> at the following example:
> >>>>
> >>>> We have an SRAT like this:
> >>>> SRAT: Node 0 PXM 0 [mem 0x00000000-0x5fffffff]
> >>>> SRAT: Node 0 PXM 0 [mem 0x100000000-0x1ffffffffff]
> >>>> SRAT: Node 1 PXM 1 [mem 0x20000000000-0x3ffffffffff]
> >>>> SRAT: Node 4 PXM 2 [mem 0x40000000000-0x5ffffffffff] hotplug
> >>>> SRAT: Node 5 PXM 3 [mem 0x60000000000-0x7ffffffffff] hotplug
> >>>> SRAT: Node 2 PXM 4 [mem 0x80000000000-0x9ffffffffff] hotplug
> >>>> SRAT: Node 3 PXM 5 [mem 0xa0000000000-0xbffffffffff] hotplug
> >>>> SRAT: Node 6 PXM 6 [mem 0xc0000000000-0xdffffffffff] hotplug
> >>>> SRAT: Node 7 PXM 7 [mem 0xe0000000000-0xfffffffffff] hotplug
> >>>>
> >>>> On boot, only node 0,1,2,3 exist.
> >>>>
> >>>> And the numa_meminfo will look like this:
> >>>> numa_meminfo.nr_blks = 9
> >>>> 1. on node 0: [0, 60000000]
> >>>> 2. on node 0: [100000000, 20000000000]
> >>>> 3. on node 1: [20000000000, 40000000000]
> >>>> 4. on node 4: [40000000000, 60000000000]
> >>>> 5. on node 5: [60000000000, 80000000000]
> >>>> 6. on node 2: [80000000000, a0000000000]
> >>>> 7. on node 3: [a0000000000, a0800000000]
> >>>> 8. on node 6: [c0000000000, a0800000000]
> >>>> 9. on node 7: [e0000000000, a0800000000]
> >>>>
> >>>> And numa_cleanup_meminfo() will merge 1 and 2, and remove 8,9 because
> >>>> the end address is over max_pfn, which is a0800000000. But 4 and 5
> >>>> are not removed because their end addresses are less then max_pfn.
> >>>> But in fact, node 4 and 5 don't exist.
> >>>>
> >>>> In a word, numa_cleanup_meminfo() is not able to handle holes between nodes.
> >>>>
> >>>> Since memory ranges in node 4 and 5 are in numa_meminfo, in numa_register_memblks(),
> >>>> node 4 and 5 will be mistakenly set to online.
> >>>>
> >>>> In this patch, we use memblock_overlaps_region() to check if ranges in
> >>>> numa_meminfo overlap with ranges in memory_block. Since memory_block contains
> >>>> all available memory at boot time, if they overlap, it means the ranges
> >>>> exist. If not, then remove them from numa_meminfo.
> >>>>
> >>> Hi Tang Chen,
> >>>
> >>> What's the impact of this problem?
> >>>
> >>> Command "numactl --hard" will show an empty node(no cpu and no memory,
> >>> but pgdat is created), right?
> >> On my box, if I run lscpu, the output looks like this:
> >>
> >> NUMA node0 CPU(s):     0-14,128-142
> >> NUMA node1 CPU(s):     15-29,143-157
> >> NUMA node2 CPU(s):
> >> NUMA node3 CPU(s):
> >> NUMA node4 CPU(s):     62-76,190-204
> >> NUMA node5 CPU(s):     78-92,206-220
> >>
> >> Node 2 and 3 are not exist, but they are online.
> >>
> >> Thanks.
> >>
> >>> Thanks,
> >>> Xishi Qiu
> >>>
> >>>> Signed-off-by: Tang Chen <tangchen@...fujitsu.com>
> >>>> ---
> >>>>    arch/x86/mm/numa.c       | 6 ++++--
> >>>>    include/linux/memblock.h | 2 ++
> >>>>    mm/memblock.c            | 2 +-
> >>>>    3 files changed, 7 insertions(+), 3 deletions(-)
> >>>>
> >>>> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> >>>> index 4053bb5..0c55cc5 100644
> >>>> --- a/arch/x86/mm/numa.c
> >>>> +++ b/arch/x86/mm/numa.c
> >>>> @@ -246,8 +246,10 @@ int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
> >>>>    		bi->start = max(bi->start, low);
> >>>>    		bi->end = min(bi->end, high);
> >>>>    
> >>>> -		/* and there's no empty block */
> >>>> -		if (bi->start >= bi->end)
> >>>> +		/* and there's no empty or non-exist block */
> >>>> +		if (bi->start >= bi->end ||
> >>>> +		    memblock_overlaps_region(&memblock.memory,
> >>>> +			bi->start, bi->end - bi->start) == -1)
> >>>>    			numa_remove_memblk_from(i--, mi);
> >>>>    	}
> >>>>    
> >>>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> >>>> index 0215ffd..3bf6cc1 100644
> >>>> --- a/include/linux/memblock.h
> >>>> +++ b/include/linux/memblock.h
> >>>> @@ -77,6 +77,8 @@ int memblock_remove(phys_addr_t base, phys_addr_t size);
> >>>>    int memblock_free(phys_addr_t base, phys_addr_t size);
> >>>>    int memblock_reserve(phys_addr_t base, phys_addr_t size);
> >>>>    void memblock_trim_memory(phys_addr_t align);
> >>>> +long memblock_overlaps_region(struct memblock_type *type,
> >>>> +			      phys_addr_t base, phys_addr_t size);
> >>>>    int memblock_mark_hotplug(phys_addr_t base, phys_addr_t size);
> >>>>    int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
> >>>>    int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> >>>> diff --git a/mm/memblock.c b/mm/memblock.c
> >>>> index 1b444c7..55b5f9f 100644
> >>>> --- a/mm/memblock.c
> >>>> +++ b/mm/memblock.c
> >>>> @@ -91,7 +91,7 @@ static unsigned long __init_memblock memblock_addrs_overlap(phys_addr_t base1, p
> >>>>    	return ((base1 < (base2 + size2)) && (base2 < (base1 + size1)));
> >>>>    }
> >>>>    
> >>>> -static long __init_memblock memblock_overlaps_region(struct memblock_type *type,
> >>>> +long __init_memblock memblock_overlaps_region(struct memblock_type *type,
> >>>>    					phys_addr_t base, phys_addr_t size)
> >>>>    {
> >>>>    	unsigned long i;
> >>>
> >>> .
> >>>
> > .
> >
> 
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