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Date: Wed, 2 Sep 2009 11:06:53 +0530
From: Ankita Garg <ankita@...ibm.com>
To: Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc: linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix fake numa on ppc
Hi Balbir,
On Tue, Sep 01, 2009 at 07:57:29PM +0530, Balbir Singh wrote:
> * Ankita Garg <ankita@...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@...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@...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@...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@...ux.vnet.ibm.com>
>
>
>
> --
> Balbir
--
Regards,
Ankita Garg (ankita@...ibm.com)
Linux Technology Center
IBM India Systems & Technology Labs,
Bangalore, India
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