Patchwork Fix fake numa on ppc

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Submitter Ankita Garg
Date Sept. 1, 2009, 9:24 a.m.
Message ID <20090901092407.GC4076@in.ibm.com>
Download mbox | patch
Permalink /patch/32732/
State Changes Requested
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Comments

Ankita Garg - Sept. 1, 2009, 9:24 a.m.
Hi Balbir,

On Tue, Sep 01, 2009 at 11:27:53AM +0530, Balbir Singh wrote:
> * Ankita Garg <ankita@in.ibm.com> [2009-09-01 10:33:16]:
> 
> > Hello,
> > 
> > Below is a patch to fix a couple of issues with fake numa node creation
> > on ppc:
> > 
> > 1) Presently, fake nodes could be created such that real numa node
> > boundaries are not respected. So a node could have lmbs that belong to
> > different real nodes.
> > 
> > 2) The cpu association is broken. On a JS22 blade for example, which is
> > a 2-node numa machine, I get the following:
> > 
> > # cat /proc/cmdline
> > root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> > # cat /sys/devices/system/node/node0/cpulist
> > 0-3
> > # cat /sys/devices/system/node/node1/cpulist
> > 4-7
> > # cat /sys/devices/system/node/node4/cpulist
> > 
> > #
> > 
> > So, though the cpus 4-7 should have been associated with node4, they
> > still belong to node1. The patch works by recording a real numa node
> > boundary and incrementing the fake node count. At the same time, a
> > mapping is stored from the real numa node to the first fake node that
> > gets created on it.
> >
> 
> Some details on how you tested it and results before and after would
> be nice. Please see git commit 1daa6d08d1257aa61f376c3cc4795660877fb9e3
> for example
> 
>

Thanks for the quick review of the patch. Here is some information on
the testing:

Tested the patch with the following commandlines:
numa=fake=2G,4G,6G,8G,10G,12G,14G,16G
numa=fake=3G,6G,10G,16G
numa=fake=4G
numa=fake=

For testing if the fake nodes respect the real node boundaries, I added
some debug printks in the node creation path. Without the patch, for the
commandline numa=fake=2G,4G,6G,8G,10G,12G,14G,16G, this is what I got:

fake id: 1 nid: 0
fake id: 1 nid: 0
...
fake id: 2 nid: 0
fake id: 2 nid: 0
...
fake id: 2 nid: 0
created new fake_node with id 3
fake id: 3 nid: 0
fake id: 3 nid: 0
...
fake id: 3 nid: 0
fake id: 3 nid: 0
fake id: 3 nid: 1
fake id: 3 nid: 1
...
created new fake_node with id 4
fake id: 4 nid: 1
fake id: 4 nid: 1
...

and so on. So, fake node 3 encompasses real node 0 & 1. Also,

# cat /sys/devices/system/node/node3/meminfo
Node 0 MemTotal:        2097152 kB
...
# # cat /sys/devices/system/node/node4/meminfo
Node 0 MemTotal:        2097152 kB
...


With the patch, I get:

fake id: 1 nid: 0
fake id: 1 nid: 0
...
fake id: 2 nid: 0
fake id: 2 nid: 0
...
fake id: 2 nid: 0
created new fake_node with id 3
fake id: 3 nid: 0
fake id: 3 nid: 0
...
fake id: 3 nid: 0
fake id: 3 nid: 0
created new fake_node with id 4
fake id: 4 nid: 1
fake id: 4 nid: 1
...

and so on. With the patch, the fake node sizes are slightly different
from that specified by the user.

# cat /sys/devices/system/node/node3/meminfo
Node 3 MemTotal:        1638400 kB
...
# cat /sys/devices/system/node/node4/meminfo
Node 4 MemTotal:         458752 kB
...

CPU association was tested as mentioned in the previous mail:

Without the patch,

# cat /proc/cmdline
root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
# cat /sys/devices/system/node/node0/cpulist
0-3
# cat /sys/devices/system/node/node1/cpulist
4-7
# cat /sys/devices/system/node/node4/cpulist

#

With the patch,

# cat /proc/cmdline
root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
# cat /sys/devices/system/node/node0/cpulist
0-3
# cat /sys/devices/system/node/node1/cpulist

# cat /sys/devices/system/node/node4/cpulist
4-7

> > 
> > Signed-off-by: Ankita Garg <ankita@in.ibm.com>
> > 
> > Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > ===================================================================
> > --- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
> > +++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > @@ -26,6 +26,11 @@
> >  #include <asm/smp.h>
> > 
> >  static int numa_enabled = 1;
> > +static int fake_enabled = 1;
> > +
> > +/* The array maps a real numa node to the first fake node that gets
> > +created on it */
> 
> Coding style is broken
> 

Fixed.

> > +int fake_numa_node_mapping[MAX_NUMNODES];
> > 
> >  static char *cmdline __initdata;
> > 
> > @@ -49,14 +54,24 @@ static int __cpuinit fake_numa_create_ne
> >  	unsigned long long mem;
> >  	char *p = cmdline;
> >  	static unsigned int fake_nid;
> > +	static unsigned int orig_nid = 0;
> 
> Should we call this prev_nid?
> 

Yes, makes sense.
> >  	static unsigned long long curr_boundary;
> > 
> >  	/*
> >  	 * Modify node id, iff we started creating NUMA nodes
> >  	 * We want to continue from where we left of the last time
> >  	 */
> > -	if (fake_nid)
> > +	if (fake_nid) {
> > +		if (orig_nid != *nid) {
> 
> OK, so this is called when the real NUMA node changes - comments would
> be nice
>

Thanks, have added the comment.
 
> > +			fake_nid++;
> > +			fake_numa_node_mapping[*nid] = fake_nid;
> > +			orig_nid = *nid;
> > +			*nid = fake_nid;
> > +			return 0;
> > +		}
> >  		*nid = fake_nid;
> > +	}
> > +
> >  	/*
> >  	 * In case there are no more arguments to parse, the
> >  	 * node_id should be the same as the last fake node id
> > @@ -440,7 +455,7 @@ static int of_drconf_to_nid_single(struc
> >   */
> >  static int __cpuinit numa_setup_cpu(unsigned long lcpu)
> >  {
> > -	int nid = 0;
> > +	int nid = 0, new_nid;
> >  	struct device_node *cpu = of_get_cpu_node(lcpu, NULL);
> > 
> >  	if (!cpu) {
> > @@ -450,8 +465,15 @@ static int __cpuinit numa_setup_cpu(unsi
> > 
> >  	nid = of_node_to_nid_single(cpu);
> > 
> > +	if (fake_enabled && nid) {
> > +		new_nid = fake_numa_node_mapping[nid];
> > +		if (new_nid > 0)
> > +			nid = new_nid;
> > +	}
> > +
> >  	if (nid < 0 || !node_online(nid))
> >  		nid = any_online_node(NODE_MASK_ALL);
> > +
> >  out:
> >  	map_cpu_to_node(lcpu, nid);
> > 
> > @@ -1005,8 +1027,11 @@ static int __init early_numa(char *p)
> >  		numa_debug = 1;
> > 
> >  	p = strstr(p, "fake=");
> > -	if (p)
> > +	if (p) {
> >  		cmdline = p + strlen("fake=");
> > +		if (numa_enabled)
> > +			fake_enabled = 1;
> 
> Have you tried passing just numa=fake= without any commandline?
> That should enable fake_enabled, but I wonder if that negatively
> impacts numa_setup_cpu(). I wonder if you should look at cmdline
> to decide on fake_enabled.
>

fake_enabled does get set even for numa=fake=. However, it does not
impact numa_setup_cpu, since fake_numa_node_mapping array would have no
mapping stored and there is a condition there already to check for the
value of the mapping. I confirmed this by booting with the above
parameter as well.

> > +	}
> > 
> >  	return 0;
> >  }
> >
> 
> Overall, I think this is the right thing to do, we need to move in
> this direction. 
> 

Heres the updated patch:

Signed-off-by: Ankita Garg <ankita@in.ibm.com>
Balbir Singh - Sept. 1, 2009, 2:27 p.m.
* Ankita Garg <ankita@in.ibm.com> [2009-09-01 14:54:07]:

> Hi Balbir,
> 
> On Tue, Sep 01, 2009 at 11:27:53AM +0530, Balbir Singh wrote:
> > * Ankita Garg <ankita@in.ibm.com> [2009-09-01 10:33:16]:
> > 
> > > Hello,
> > > 
> > > Below is a patch to fix a couple of issues with fake numa node creation
> > > on ppc:
> > > 
> > > 1) Presently, fake nodes could be created such that real numa node
> > > boundaries are not respected. So a node could have lmbs that belong to
> > > different real nodes.
> > > 
> > > 2) The cpu association is broken. On a JS22 blade for example, which is
> > > a 2-node numa machine, I get the following:
> > > 
> > > # cat /proc/cmdline
> > > root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> > > # cat /sys/devices/system/node/node0/cpulist
> > > 0-3
> > > # cat /sys/devices/system/node/node1/cpulist
> > > 4-7
> > > # cat /sys/devices/system/node/node4/cpulist
> > > 
> > > #
> > > 
> > > So, though the cpus 4-7 should have been associated with node4, they
> > > still belong to node1. The patch works by recording a real numa node
> > > boundary and incrementing the fake node count. At the same time, a
> > > mapping is stored from the real numa node to the first fake node that
> > > gets created on it.
> > >
> > 
> > Some details on how you tested it and results before and after would
> > be nice. Please see git commit 1daa6d08d1257aa61f376c3cc4795660877fb9e3
> > for example
> > 
> >
> 
> Thanks for the quick review of the patch. Here is some information on
> the testing:
> 
> Tested the patch with the following commandlines:
> numa=fake=2G,4G,6G,8G,10G,12G,14G,16G
> numa=fake=3G,6G,10G,16G
> numa=fake=4G
> numa=fake=
> 
> For testing if the fake nodes respect the real node boundaries, I added
> some debug printks in the node creation path. Without the patch, for the
> commandline numa=fake=2G,4G,6G,8G,10G,12G,14G,16G, this is what I got:
> 
> fake id: 1 nid: 0
> fake id: 1 nid: 0
> ...
> fake id: 2 nid: 0
> fake id: 2 nid: 0
> ...
> fake id: 2 nid: 0
> created new fake_node with id 3
> fake id: 3 nid: 0
> fake id: 3 nid: 0
> ...
> fake id: 3 nid: 0
> fake id: 3 nid: 0
> fake id: 3 nid: 1
> fake id: 3 nid: 1
> ...
> created new fake_node with id 4
> fake id: 4 nid: 1
> fake id: 4 nid: 1
> ...
> 
> and so on. So, fake node 3 encompasses real node 0 & 1. Also,
> 
> # cat /sys/devices/system/node/node3/meminfo
> Node 0 MemTotal:        2097152 kB
> ...
> # # cat /sys/devices/system/node/node4/meminfo
> Node 0 MemTotal:        2097152 kB
> ...
> 
> 
> With the patch, I get:
> 
> fake id: 1 nid: 0
> fake id: 1 nid: 0
> ...
> fake id: 2 nid: 0
> fake id: 2 nid: 0
> ...
> fake id: 2 nid: 0
> created new fake_node with id 3
> fake id: 3 nid: 0
> fake id: 3 nid: 0
> ...
> fake id: 3 nid: 0
> fake id: 3 nid: 0
> created new fake_node with id 4
> fake id: 4 nid: 1
> fake id: 4 nid: 1
> ...
> 
> and so on. With the patch, the fake node sizes are slightly different
> from that specified by the user.
> 
> # cat /sys/devices/system/node/node3/meminfo
> Node 3 MemTotal:        1638400 kB
> ...
> # cat /sys/devices/system/node/node4/meminfo
> Node 4 MemTotal:         458752 kB
> ...
> 
> CPU association was tested as mentioned in the previous mail:
> 
> Without the patch,
> 
> # cat /proc/cmdline
> root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> # cat /sys/devices/system/node/node0/cpulist
> 0-3
> # cat /sys/devices/system/node/node1/cpulist
> 4-7
> # cat /sys/devices/system/node/node4/cpulist
> 
> #
> 
> With the patch,
> 
> # cat /proc/cmdline
> root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> # cat /sys/devices/system/node/node0/cpulist
> 0-3
> # cat /sys/devices/system/node/node1/cpulist
> 

Oh! interesting.. cpuless nodes :) I think we need to fix this in the
longer run and distribute cpus between fake numa nodes of a real node
using some acceptable heuristic.

> # cat /sys/devices/system/node/node4/cpulist
> 4-7
> 
> > > 
> > > Signed-off-by: Ankita Garg <ankita@in.ibm.com>
> > > 
> > > Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > > ===================================================================
> > > --- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
> > > +++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > > @@ -26,6 +26,11 @@
> > >  #include <asm/smp.h>
> > > 
> > >  static int numa_enabled = 1;
> > > +static int fake_enabled = 1;
> > > +
> > > +/* The array maps a real numa node to the first fake node that gets
> > > +created on it */
> > 
> > Coding style is broken
> > 
> 
> Fixed.
> 
> > > +int fake_numa_node_mapping[MAX_NUMNODES];
> > > 
> > >  static char *cmdline __initdata;
> > > 
> > > @@ -49,14 +54,24 @@ static int __cpuinit fake_numa_create_ne
> > >  	unsigned long long mem;
> > >  	char *p = cmdline;
> > >  	static unsigned int fake_nid;
> > > +	static unsigned int orig_nid = 0;
> > 
> > Should we call this prev_nid?
> > 
> 
> Yes, makes sense.
> > >  	static unsigned long long curr_boundary;
> > > 
> > >  	/*
> > >  	 * Modify node id, iff we started creating NUMA nodes
> > >  	 * We want to continue from where we left of the last time
> > >  	 */
> > > -	if (fake_nid)
> > > +	if (fake_nid) {
> > > +		if (orig_nid != *nid) {
> > 
> > OK, so this is called when the real NUMA node changes - comments would
> > be nice
> >
> 
> Thanks, have added the comment.
> 
> > > +			fake_nid++;
> > > +			fake_numa_node_mapping[*nid] = fake_nid;
> > > +			orig_nid = *nid;
> > > +			*nid = fake_nid;
> > > +			return 0;
> > > +		}
> > >  		*nid = fake_nid;
> > > +	}
> > > +
> > >  	/*
> > >  	 * In case there are no more arguments to parse, the
> > >  	 * node_id should be the same as the last fake node id
> > > @@ -440,7 +455,7 @@ static int of_drconf_to_nid_single(struc
> > >   */
> > >  static int __cpuinit numa_setup_cpu(unsigned long lcpu)
> > >  {
> > > -	int nid = 0;
> > > +	int nid = 0, new_nid;
> > >  	struct device_node *cpu = of_get_cpu_node(lcpu, NULL);
> > > 
> > >  	if (!cpu) {
> > > @@ -450,8 +465,15 @@ static int __cpuinit numa_setup_cpu(unsi
> > > 
> > >  	nid = of_node_to_nid_single(cpu);
> > > 
> > > +	if (fake_enabled && nid) {
> > > +		new_nid = fake_numa_node_mapping[nid];
> > > +		if (new_nid > 0)
> > > +			nid = new_nid;
> > > +	}
> > > +
> > >  	if (nid < 0 || !node_online(nid))
> > >  		nid = any_online_node(NODE_MASK_ALL);
> > > +
> > >  out:
> > >  	map_cpu_to_node(lcpu, nid);
> > > 
> > > @@ -1005,8 +1027,11 @@ static int __init early_numa(char *p)
> > >  		numa_debug = 1;
> > > 
> > >  	p = strstr(p, "fake=");
> > > -	if (p)
> > > +	if (p) {
> > >  		cmdline = p + strlen("fake=");
> > > +		if (numa_enabled)
> > > +			fake_enabled = 1;
> > 
> > Have you tried passing just numa=fake= without any commandline?
> > That should enable fake_enabled, but I wonder if that negatively
> > impacts numa_setup_cpu(). I wonder if you should look at cmdline
> > to decide on fake_enabled.
> >
> 
> fake_enabled does get set even for numa=fake=. However, it does not
> impact numa_setup_cpu, since fake_numa_node_mapping array would have no
> mapping stored and there is a condition there already to check for the
> value of the mapping. I confirmed this by booting with the above
> parameter as well.
> 
> > > +	}
> > > 
> > >  	return 0;
> > >  }
> > >
> > 
> > Overall, I think this is the right thing to do, we need to move in
> > this direction. 
> > 
> 
> Heres the updated patch:
> 
> Signed-off-by: Ankita Garg <ankita@in.ibm.com> 
> 
> Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> ===================================================================
> --- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
> +++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> @@ -26,6 +26,13 @@
>  #include <asm/smp.h>
> 
>  static int numa_enabled = 1;
> +static int fake_enabled = 1;
> +
> +/*
> + * The array maps a real numa node to the first fake node that gets
> + * created on it
> + */
> +int fake_numa_node_mapping[MAX_NUMNODES];
> 
>  static char *cmdline __initdata;
> 
> @@ -49,14 +56,29 @@ static int __cpuinit fake_numa_create_ne
>  	unsigned long long mem;
>  	char *p = cmdline;
>  	static unsigned int fake_nid;
> +	static unsigned int prev_nid = 0;
>  	static unsigned long long curr_boundary;
> 
>  	/*
>  	 * Modify node id, iff we started creating NUMA nodes
>  	 * We want to continue from where we left of the last time
>  	 */
> -	if (fake_nid)
> +	if (fake_nid) {
> +		/*
> +		 * Moved over to the next real numa node, increment fake
> +		 * node number and store the mapping of the real node to
> +		 * the fake node
> +		 */
> +		if (prev_nid != *nid) {
> +			fake_nid++;
> +			fake_numa_node_mapping[*nid] = fake_nid;
> +			prev_nid = *nid;
> +			*nid = fake_nid;
> +			return 0;
> +		}
>  		*nid = fake_nid;
> +	}
> +
>  	/*
>  	 * In case there are no more arguments to parse, the
>  	 * node_id should be the same as the last fake node id
> @@ -440,7 +462,7 @@ static int of_drconf_to_nid_single(struc
>   */
>  static int __cpuinit numa_setup_cpu(unsigned long lcpu)
>  {
> -	int nid = 0;
> +	int nid = 0, new_nid;
>  	struct device_node *cpu = of_get_cpu_node(lcpu, NULL);
> 
>  	if (!cpu) {
> @@ -450,8 +472,15 @@ static int __cpuinit numa_setup_cpu(unsi
> 
>  	nid = of_node_to_nid_single(cpu);
> 
> +	if (fake_enabled && nid) {
> +		new_nid = fake_numa_node_mapping[nid];
> +		if (new_nid > 0)
> +			nid = new_nid;
> +	}
> +
>  	if (nid < 0 || !node_online(nid))
>  		nid = any_online_node(NODE_MASK_ALL);
> +
>  out:
>  	map_cpu_to_node(lcpu, nid);
> 
> @@ -1005,8 +1034,12 @@ static int __init early_numa(char *p)
>  		numa_debug = 1;
> 
>  	p = strstr(p, "fake=");
> -	if (p)
> +	if (p) {
>  		cmdline = p + strlen("fake=");
> +		if (numa_enabled) {
> +			fake_enabled = 1;
> +		}
> +	}
> 
>  	return 0;
>  }
>


Looks good to me


Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Ankita Garg - Sept. 2, 2009, 5:36 a.m.
Hi Balbir,

On Tue, Sep 01, 2009 at 07:57:29PM +0530, Balbir Singh wrote:
> * Ankita Garg <ankita@in.ibm.com> [2009-09-01 14:54:07]:
> 
> > Hi Balbir,
> > 
> > On Tue, Sep 01, 2009 at 11:27:53AM +0530, Balbir Singh wrote:
> > > * Ankita Garg <ankita@in.ibm.com> [2009-09-01 10:33:16]:
> > > 
> > > > Hello,
> > > > 
> > > > Below is a patch to fix a couple of issues with fake numa node creation
> > > > on ppc:
> > > > 
> > > > 1) Presently, fake nodes could be created such that real numa node
> > > > boundaries are not respected. So a node could have lmbs that belong to
> > > > different real nodes.
> > > > 
> > > > 2) The cpu association is broken. On a JS22 blade for example, which is
> > > > a 2-node numa machine, I get the following:
> > > > 
> > > > # cat /proc/cmdline
> > > > root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> > > > # cat /sys/devices/system/node/node0/cpulist
> > > > 0-3
> > > > # cat /sys/devices/system/node/node1/cpulist
> > > > 4-7
> > > > # cat /sys/devices/system/node/node4/cpulist
> > > > 
> > > > #
> > > > 
> > > > So, though the cpus 4-7 should have been associated with node4, they
> > > > still belong to node1. The patch works by recording a real numa node
> > > > boundary and incrementing the fake node count. At the same time, a
> > > > mapping is stored from the real numa node to the first fake node that
> > > > gets created on it.
> > > >
> > > 
> > > Some details on how you tested it and results before and after would
> > > be nice. Please see git commit 1daa6d08d1257aa61f376c3cc4795660877fb9e3
> > > for example
> > > 
> > >
> > 
> > Thanks for the quick review of the patch. Here is some information on
> > the testing:
> > 
> > Tested the patch with the following commandlines:
> > numa=fake=2G,4G,6G,8G,10G,12G,14G,16G
> > numa=fake=3G,6G,10G,16G
> > numa=fake=4G
> > numa=fake=
> > 
> > For testing if the fake nodes respect the real node boundaries, I added
> > some debug printks in the node creation path. Without the patch, for the
> > commandline numa=fake=2G,4G,6G,8G,10G,12G,14G,16G, this is what I got:
> > 
> > fake id: 1 nid: 0
> > fake id: 1 nid: 0
> > ...
> > fake id: 2 nid: 0
> > fake id: 2 nid: 0
> > ...
> > fake id: 2 nid: 0
> > created new fake_node with id 3
> > fake id: 3 nid: 0
> > fake id: 3 nid: 0
> > ...
> > fake id: 3 nid: 0
> > fake id: 3 nid: 0
> > fake id: 3 nid: 1
> > fake id: 3 nid: 1
> > ...
> > created new fake_node with id 4
> > fake id: 4 nid: 1
> > fake id: 4 nid: 1
> > ...
> > 
> > and so on. So, fake node 3 encompasses real node 0 & 1. Also,
> > 
> > # cat /sys/devices/system/node/node3/meminfo
> > Node 0 MemTotal:        2097152 kB
> > ...
> > # # cat /sys/devices/system/node/node4/meminfo
> > Node 0 MemTotal:        2097152 kB
> > ...
> > 
> > 
> > With the patch, I get:
> > 
> > fake id: 1 nid: 0
> > fake id: 1 nid: 0
> > ...
> > fake id: 2 nid: 0
> > fake id: 2 nid: 0
> > ...
> > fake id: 2 nid: 0
> > created new fake_node with id 3
> > fake id: 3 nid: 0
> > fake id: 3 nid: 0
> > ...
> > fake id: 3 nid: 0
> > fake id: 3 nid: 0
> > created new fake_node with id 4
> > fake id: 4 nid: 1
> > fake id: 4 nid: 1
> > ...
> > 
> > and so on. With the patch, the fake node sizes are slightly different
> > from that specified by the user.
> > 
> > # cat /sys/devices/system/node/node3/meminfo
> > Node 3 MemTotal:        1638400 kB
> > ...
> > # cat /sys/devices/system/node/node4/meminfo
> > Node 4 MemTotal:         458752 kB
> > ...
> > 
> > CPU association was tested as mentioned in the previous mail:
> > 
> > Without the patch,
> > 
> > # cat /proc/cmdline
> > root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> > # cat /sys/devices/system/node/node0/cpulist
> > 0-3
> > # cat /sys/devices/system/node/node1/cpulist
> > 4-7
> > # cat /sys/devices/system/node/node4/cpulist
> > 
> > #
> > 
> > With the patch,
> > 
> > # cat /proc/cmdline
> > root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> > # cat /sys/devices/system/node/node0/cpulist
> > 0-3
> > # cat /sys/devices/system/node/node1/cpulist
> > 
> 
> Oh! interesting.. cpuless nodes :) I think we need to fix this in the
> longer run and distribute cpus between fake numa nodes of a real node
> using some acceptable heuristic.
>

True. Presently this is broken on both x86 and ppc systems. It would be
interesting to find a way to map, for example, 4 cpus to >4 number of
fake nodes created from a single real numa node!
 
> > # cat /sys/devices/system/node/node4/cpulist
> > 4-7
> > 
> > > > 
> > > > Signed-off-by: Ankita Garg <ankita@in.ibm.com>
> > > > 
> > > > Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > > > ===================================================================
> > > > --- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
> > > > +++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > > > @@ -26,6 +26,11 @@
> > > >  #include <asm/smp.h>
> > > > 
> > > >  static int numa_enabled = 1;
> > > > +static int fake_enabled = 1;
> > > > +
> > > > +/* The array maps a real numa node to the first fake node that gets
> > > > +created on it */
> > > 
> > > Coding style is broken
> > > 
> > 
> > Fixed.
> > 
> > > > +int fake_numa_node_mapping[MAX_NUMNODES];
> > > > 
> > > >  static char *cmdline __initdata;
> > > > 
> > > > @@ -49,14 +54,24 @@ static int __cpuinit fake_numa_create_ne
> > > >  	unsigned long long mem;
> > > >  	char *p = cmdline;
> > > >  	static unsigned int fake_nid;
> > > > +	static unsigned int orig_nid = 0;
> > > 
> > > Should we call this prev_nid?
> > > 
> > 
> > Yes, makes sense.
> > > >  	static unsigned long long curr_boundary;
> > > > 
> > > >  	/*
> > > >  	 * Modify node id, iff we started creating NUMA nodes
> > > >  	 * We want to continue from where we left of the last time
> > > >  	 */
> > > > -	if (fake_nid)
> > > > +	if (fake_nid) {
> > > > +		if (orig_nid != *nid) {
> > > 
> > > OK, so this is called when the real NUMA node changes - comments would
> > > be nice
> > >
> > 
> > Thanks, have added the comment.
> > 
> > > > +			fake_nid++;
> > > > +			fake_numa_node_mapping[*nid] = fake_nid;
> > > > +			orig_nid = *nid;
> > > > +			*nid = fake_nid;
> > > > +			return 0;
> > > > +		}
> > > >  		*nid = fake_nid;
> > > > +	}
> > > > +
> > > >  	/*
> > > >  	 * In case there are no more arguments to parse, the
> > > >  	 * node_id should be the same as the last fake node id
> > > > @@ -440,7 +455,7 @@ static int of_drconf_to_nid_single(struc
> > > >   */
> > > >  static int __cpuinit numa_setup_cpu(unsigned long lcpu)
> > > >  {
> > > > -	int nid = 0;
> > > > +	int nid = 0, new_nid;
> > > >  	struct device_node *cpu = of_get_cpu_node(lcpu, NULL);
> > > > 
> > > >  	if (!cpu) {
> > > > @@ -450,8 +465,15 @@ static int __cpuinit numa_setup_cpu(unsi
> > > > 
> > > >  	nid = of_node_to_nid_single(cpu);
> > > > 
> > > > +	if (fake_enabled && nid) {
> > > > +		new_nid = fake_numa_node_mapping[nid];
> > > > +		if (new_nid > 0)
> > > > +			nid = new_nid;
> > > > +	}
> > > > +
> > > >  	if (nid < 0 || !node_online(nid))
> > > >  		nid = any_online_node(NODE_MASK_ALL);
> > > > +
> > > >  out:
> > > >  	map_cpu_to_node(lcpu, nid);
> > > > 
> > > > @@ -1005,8 +1027,11 @@ static int __init early_numa(char *p)
> > > >  		numa_debug = 1;
> > > > 
> > > >  	p = strstr(p, "fake=");
> > > > -	if (p)
> > > > +	if (p) {
> > > >  		cmdline = p + strlen("fake=");
> > > > +		if (numa_enabled)
> > > > +			fake_enabled = 1;
> > > 
> > > Have you tried passing just numa=fake= without any commandline?
> > > That should enable fake_enabled, but I wonder if that negatively
> > > impacts numa_setup_cpu(). I wonder if you should look at cmdline
> > > to decide on fake_enabled.
> > >
> > 
> > fake_enabled does get set even for numa=fake=. However, it does not
> > impact numa_setup_cpu, since fake_numa_node_mapping array would have no
> > mapping stored and there is a condition there already to check for the
> > value of the mapping. I confirmed this by booting with the above
> > parameter as well.
> > 
> > > > +	}
> > > > 
> > > >  	return 0;
> > > >  }
> > > >
> > > 
> > > Overall, I think this is the right thing to do, we need to move in
> > > this direction. 
> > > 
> > 
> > Heres the updated patch:
> > 
> > Signed-off-by: Ankita Garg <ankita@in.ibm.com> 
> > 
> > Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > ===================================================================
> > --- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
> > +++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > @@ -26,6 +26,13 @@
> >  #include <asm/smp.h>
> > 
> >  static int numa_enabled = 1;
> > +static int fake_enabled = 1;
> > +
> > +/*
> > + * The array maps a real numa node to the first fake node that gets
> > + * created on it
> > + */
> > +int fake_numa_node_mapping[MAX_NUMNODES];
> > 
> >  static char *cmdline __initdata;
> > 
> > @@ -49,14 +56,29 @@ static int __cpuinit fake_numa_create_ne
> >  	unsigned long long mem;
> >  	char *p = cmdline;
> >  	static unsigned int fake_nid;
> > +	static unsigned int prev_nid = 0;
> >  	static unsigned long long curr_boundary;
> > 
> >  	/*
> >  	 * Modify node id, iff we started creating NUMA nodes
> >  	 * We want to continue from where we left of the last time
> >  	 */
> > -	if (fake_nid)
> > +	if (fake_nid) {
> > +		/*
> > +		 * Moved over to the next real numa node, increment fake
> > +		 * node number and store the mapping of the real node to
> > +		 * the fake node
> > +		 */
> > +		if (prev_nid != *nid) {
> > +			fake_nid++;
> > +			fake_numa_node_mapping[*nid] = fake_nid;
> > +			prev_nid = *nid;
> > +			*nid = fake_nid;
> > +			return 0;
> > +		}
> >  		*nid = fake_nid;
> > +	}
> > +
> >  	/*
> >  	 * In case there are no more arguments to parse, the
> >  	 * node_id should be the same as the last fake node id
> > @@ -440,7 +462,7 @@ static int of_drconf_to_nid_single(struc
> >   */
> >  static int __cpuinit numa_setup_cpu(unsigned long lcpu)
> >  {
> > -	int nid = 0;
> > +	int nid = 0, new_nid;
> >  	struct device_node *cpu = of_get_cpu_node(lcpu, NULL);
> > 
> >  	if (!cpu) {
> > @@ -450,8 +472,15 @@ static int __cpuinit numa_setup_cpu(unsi
> > 
> >  	nid = of_node_to_nid_single(cpu);
> > 
> > +	if (fake_enabled && nid) {
> > +		new_nid = fake_numa_node_mapping[nid];
> > +		if (new_nid > 0)
> > +			nid = new_nid;
> > +	}
> > +
> >  	if (nid < 0 || !node_online(nid))
> >  		nid = any_online_node(NODE_MASK_ALL);
> > +
> >  out:
> >  	map_cpu_to_node(lcpu, nid);
> > 
> > @@ -1005,8 +1034,12 @@ static int __init early_numa(char *p)
> >  		numa_debug = 1;
> > 
> >  	p = strstr(p, "fake=");
> > -	if (p)
> > +	if (p) {
> >  		cmdline = p + strlen("fake=");
> > +		if (numa_enabled) {
> > +			fake_enabled = 1;
> > +		}
> > +	}
> > 
> >  	return 0;
> >  }
> >
> 
> 
> Looks good to me
> 
> 
> Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> 
> 
> 
> -- 
> 	Balbir
Benjamin Herrenschmidt - Sept. 2, 2009, 5:52 a.m.
On Tue, 2009-09-01 at 19:57 +0530, Balbir Singh wrote:

> > 
> > Heres the updated patch:
> > 
> > Signed-off-by: Ankita Garg <ankita@in.ibm.com> 

The thread is too messy. Please Ankita can you re-submit in proper
form (ie. subject, cset, signed-off & patch) please ?

In general, don't mix reply to comments and new patch submission,
or patchwork gets really confuse. Post a new name, with something
like [PATCH v2] <name of the patch> in the subject.

Thanks.

Cheers,
Ben.

> > Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > ===================================================================
> > --- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
> > +++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
> > @@ -26,6 +26,13 @@
> >  #include <asm/smp.h>
> > 
> >  static int numa_enabled = 1;
> > +static int fake_enabled = 1;
> > +
> > +/*
> > + * The array maps a real numa node to the first fake node that gets
> > + * created on it
> > + */
> > +int fake_numa_node_mapping[MAX_NUMNODES];
> > 
> >  static char *cmdline __initdata;
> > 
> > @@ -49,14 +56,29 @@ static int __cpuinit fake_numa_create_ne
> >  	unsigned long long mem;
> >  	char *p = cmdline;
> >  	static unsigned int fake_nid;
> > +	static unsigned int prev_nid = 0;
> >  	static unsigned long long curr_boundary;
> > 
> >  	/*
> >  	 * Modify node id, iff we started creating NUMA nodes
> >  	 * We want to continue from where we left of the last time
> >  	 */
> > -	if (fake_nid)
> > +	if (fake_nid) {
> > +		/*
> > +		 * Moved over to the next real numa node, increment fake
> > +		 * node number and store the mapping of the real node to
> > +		 * the fake node
> > +		 */
> > +		if (prev_nid != *nid) {
> > +			fake_nid++;
> > +			fake_numa_node_mapping[*nid] = fake_nid;
> > +			prev_nid = *nid;
> > +			*nid = fake_nid;
> > +			return 0;
> > +		}
> >  		*nid = fake_nid;
> > +	}
> > +
> >  	/*
> >  	 * In case there are no more arguments to parse, the
> >  	 * node_id should be the same as the last fake node id
> > @@ -440,7 +462,7 @@ static int of_drconf_to_nid_single(struc
> >   */
> >  static int __cpuinit numa_setup_cpu(unsigned long lcpu)
> >  {
> > -	int nid = 0;
> > +	int nid = 0, new_nid;
> >  	struct device_node *cpu = of_get_cpu_node(lcpu, NULL);
> > 
> >  	if (!cpu) {
> > @@ -450,8 +472,15 @@ static int __cpuinit numa_setup_cpu(unsi
> > 
> >  	nid = of_node_to_nid_single(cpu);
> > 
> > +	if (fake_enabled && nid) {
> > +		new_nid = fake_numa_node_mapping[nid];
> > +		if (new_nid > 0)
> > +			nid = new_nid;
> > +	}
> > +
> >  	if (nid < 0 || !node_online(nid))
> >  		nid = any_online_node(NODE_MASK_ALL);
> > +
> >  out:
> >  	map_cpu_to_node(lcpu, nid);
> > 
> > @@ -1005,8 +1034,12 @@ static int __init early_numa(char *p)
> >  		numa_debug = 1;
> > 
> >  	p = strstr(p, "fake=");
> > -	if (p)
> > +	if (p) {
> >  		cmdline = p + strlen("fake=");
> > +		if (numa_enabled) {
> > +			fake_enabled = 1;
> > +		}
> > +	}
> > 
> >  	return 0;
> >  }
> >
> 
> 
> Looks good to me
> 
> 
> Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
>  
> 
>
Benjamin Herrenschmidt - Sept. 2, 2009, 5:53 a.m.
On Wed, 2009-09-02 at 11:06 +0530, Ankita Garg wrote:
> > Oh! interesting.. cpuless nodes :) I think we need to fix this in the
> > longer run and distribute cpus between fake numa nodes of a real node
> > using some acceptable heuristic.
> >
> 
> True. Presently this is broken on both x86 and ppc systems. It would be
> interesting to find a way to map, for example, 4 cpus to >4 number of
> fake nodes created from a single real numa node!

Since I'm pretty sure there could be CPU less nodes just like there
could be memory-less nodes, it would be good if fake numa could
simulate them too :-)

Cheers,
Ben.
David Rientjes - Sept. 2, 2009, 5:58 a.m.
On Wed, 2 Sep 2009, Ankita Garg wrote:

> > > With the patch,
> > > 
> > > # cat /proc/cmdline
> > > root=/dev/sda6  numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
> > > # cat /sys/devices/system/node/node0/cpulist
> > > 0-3
> > > # cat /sys/devices/system/node/node1/cpulist
> > > 
> > 
> > Oh! interesting.. cpuless nodes :) I think we need to fix this in the
> > longer run and distribute cpus between fake numa nodes of a real node
> > using some acceptable heuristic.
> >
> 
> True. Presently this is broken on both x86 and ppc systems. It would be
> interesting to find a way to map, for example, 4 cpus to >4 number of
> fake nodes created from a single real numa node!
>  

We've done it for years on x86_64.  It's quite trivial to map all fake 
nodes within a physical node to the cpus to which they have affinity both 
via node_to_cpumask_map() and cpu_to_node_map().  There should be no 
kernel space dependencies on a cpu appearing in only a single node's 
cpumask and if you map each fake node to its physical node's pxm, you can 
index into the slit and generate local NUMA distances amongst fake nodes.

So if you map the apicids and pxms appropriately depending on the 
physical topology of the machine, that is the only emulation necessary on 
x86_64 for the page allocator zonelist ordering, task migration, etc.  (If 
you use CONFIG_SLAB, you'll need to avoid the exponential growth of alien 
caches, but that's an implementation detail and isn't really within the 
scope of numa=fake's purpose to modify.)
David Rientjes - Sept. 2, 2009, 6:03 a.m.
On Wed, 2 Sep 2009, Benjamin Herrenschmidt wrote:

> Since I'm pretty sure there could be CPU less nodes just like there
> could be memory-less nodes, it would be good if fake numa could
> simulate them too :-)
> 

You don't want to simulate cpu less nodes since they do have affinity to 
ranges of memory, you want to map each fake node to a cpumask including 
all cpus with affinity to its memory, map each cpu to one fake node (with 
memory) that it has physical affinity to, and then give all fake nodes 
local NUMA distance to those on the same physical node.  Memoryless nodes 
take care of themselves since they rely purely on node_distance(), so the 
index into the slit for all fake nodes to those without memory will be the 
same.
Benjamin Herrenschmidt - Sept. 2, 2009, 8:51 a.m.
On Tue, 2009-09-01 at 23:03 -0700, David Rientjes wrote:
> On Wed, 2 Sep 2009, Benjamin Herrenschmidt wrote:
> 
> > Since I'm pretty sure there could be CPU less nodes just like there
> > could be memory-less nodes, it would be good if fake numa could
> > simulate them too :-)
> > 
> 
> You don't want to simulate cpu less nodes since they do have affinity to 
> ranges of memory, you want to map each fake node to a cpumask including 
> all cpus with affinity to its memory, map each cpu to one fake node (with 
> memory) that it has physical affinity to, and then give all fake nodes 
> local NUMA distance to those on the same physical node.  Memoryless nodes 
> take care of themselves since they rely purely on node_distance(), so the 
> index into the slit for all fake nodes to those without memory will be the 
> same.

Ok, makes sense, thanks.

Cheers,
Ben.

Patch

Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
===================================================================
--- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
+++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
@@ -26,6 +26,13 @@ 
 #include <asm/smp.h>
 
 static int numa_enabled = 1;
+static int fake_enabled = 1;
+
+/*
+ * The array maps a real numa node to the first fake node that gets
+ * created on it
+ */
+int fake_numa_node_mapping[MAX_NUMNODES];
 
 static char *cmdline __initdata;
 
@@ -49,14 +56,29 @@  static int __cpuinit fake_numa_create_ne
 	unsigned long long mem;
 	char *p = cmdline;
 	static unsigned int fake_nid;
+	static unsigned int prev_nid = 0;
 	static unsigned long long curr_boundary;
 
 	/*
 	 * Modify node id, iff we started creating NUMA nodes
 	 * We want to continue from where we left of the last time
 	 */
-	if (fake_nid)
+	if (fake_nid) {
+		/*
+		 * Moved over to the next real numa node, increment fake
+		 * node number and store the mapping of the real node to
+		 * the fake node
+		 */
+		if (prev_nid != *nid) {
+			fake_nid++;
+			fake_numa_node_mapping[*nid] = fake_nid;
+			prev_nid = *nid;
+			*nid = fake_nid;
+			return 0;
+		}
 		*nid = fake_nid;
+	}
+
 	/*
 	 * In case there are no more arguments to parse, the
 	 * node_id should be the same as the last fake node id
@@ -440,7 +462,7 @@  static int of_drconf_to_nid_single(struc
  */
 static int __cpuinit numa_setup_cpu(unsigned long lcpu)
 {
-	int nid = 0;
+	int nid = 0, new_nid;
 	struct device_node *cpu = of_get_cpu_node(lcpu, NULL);
 
 	if (!cpu) {
@@ -450,8 +472,15 @@  static int __cpuinit numa_setup_cpu(unsi
 
 	nid = of_node_to_nid_single(cpu);
 
+	if (fake_enabled && nid) {
+		new_nid = fake_numa_node_mapping[nid];
+		if (new_nid > 0)
+			nid = new_nid;
+	}
+
 	if (nid < 0 || !node_online(nid))
 		nid = any_online_node(NODE_MASK_ALL);
+
 out:
 	map_cpu_to_node(lcpu, nid);
 
@@ -1005,8 +1034,12 @@  static int __init early_numa(char *p)
 		numa_debug = 1;
 
 	p = strstr(p, "fake=");
-	if (p)
+	if (p) {
 		cmdline = p + strlen("fake=");
+		if (numa_enabled) {
+			fake_enabled = 1;
+		}
+	}
 
 	return 0;
 }