The attached represents an initial stab at implementing topology functions (or
actually indirecting topology through the subarchitecture features).
Getting this far made me realise that the current topology infrastructure is
rather inadequate (being geared towards the needs of NUMA machines).
All I really need for voyager is the concept of cpu_nodes (voyager CPU cards
have huge L3 caches and up to 4 CPUs each, so scheduling between CPU cards can
end up rather expensive in terms of cache invalidation). I have no use for
memory affinities since the voyager memory map is uniform.
I'd like to rework the current sysfs cpu/node pieces to provide two separate
topologies (one for CPU and one for memory).
Ultimately, the scheduler could be tuned to use the topologies to make
scheduling decisions. When that happens, we can probably fold the current
Pentium Hyperthreading stuff into a simple topology map as well.
I believe Martin Bligh and Bill Irwin are working (or at least thinking)
somewhat along these lines, so I thought I'd gather feedback before jumping
into a wholesale rewrite.
James Bottomley
> I'd like to rework the current sysfs cpu/node pieces to provide
> two separate topologies (one for CPU and one for memory).
There are two other sets of patches that are floating around that
will interact with this. The first (from Matt) makes the topo
functions cache results, instead of recalculating each time.
I'm thinking that we may want the generic front end to do that and
read from arrays, whilst only the *_init backend gets moved into
the subarch stuff ? (looking back at the patch right now, I can't
quite see what it's doing in 30s, but that's what it was meant to do).
The second is the start of breaking things out into the numaq
subarch - the attatched bits seem to work & are written with the
intent of being mergeable. It's just pieces torn off the big patch
by James Cleverdon and John Stultz (which isn't really mergeable
as is) and tweaked around by me. I'm going to test them a little
more before submission, but they're pretty much there, I think.
They're based on top of John's subarch reshuffle (the stuff you had
under generic is really NUMA-Q)
> Ultimately, the scheduler could be tuned to use the topologies to
> make scheduling decisions.
We kind of have that already. There are NUMA sceduler patches that
do this kind of thing in 2.5.47-mjb3 ... earlier versions of Erich's
scheduler had a pooling abstraction - this got ripped out for
simplicity in the hope of getting something merged before the 2.5
freeze, but it'd be nice to put them back if that's not going to
happen (still vaguely hoping).
> When that happens, we can probably fold
> the current Pentium Hyperthreading stuff into a simple topology map
> as well.
Not sure about that ... the HT stuff I believe created one queue
per pair of CPUs, which isn't going to work well for multiple real
CPUs per nodes, though is kind of a nice trick for a shared cache
SMT like HT .... things like the PPC64 chip multi-chip-on-1-die
may feel differently about that.
> I believe Martin Bligh and Bill Irwin are working (or at least
> thinking) somewhat along these lines, so I thought I'd gather
> feedback before jumping into a wholesale rewrite.
cc'ed John, Erich, Matt ...
M.
James Bottomley wrote:
> The attached represents an initial stab at implementing topology functions (or
> actually indirecting topology through the subarchitecture features).
Hmm.. I think this is actually a really good goal. I've got some
comments on your implementation below, but I think this goes in the
right direction.
> Getting this far made me realise that the current topology infrastructure is
> rather inadequate (being geared towards the needs of NUMA machines).
>
> All I really need for voyager is the concept of cpu_nodes (voyager CPU cards
> have huge L3 caches and up to 4 CPUs each, so scheduling between CPU cards can
> end up rather expensive in terms of cache invalidation). I have no use for
> memory affinities since the voyager memory map is uniform.
Inadequate? It sounds as though the current topology infrastructure
does everything you need plus *more*. In that case, simply don't use
that part you don't need (memory affinity), and you get the part you do
need (CPU affinity) for free. No?
> I'd like to rework the current sysfs cpu/node pieces to provide two separate
> topologies (one for CPU and one for memory).
If you don't want the memblk stuff in for voyager, just edit the
makefile, and make sure drivers/base/memblk.c isn't compiled in for you.
Or, even more simply, when you write the topology init for voyager,
don't initialize any memblks... problem solved! ;)
> Ultimately, the scheduler could be tuned to use the topologies to make
> scheduling decisions. When that happens, we can probably fold the current
> Pentium Hyperthreading stuff into a simple topology map as well.
>
> I believe Martin Bligh and Bill Irwin are working (or at least thinking)
> somewhat along these lines, so I thought I'd gather feedback before jumping
> into a wholesale rewrite.
Martin already responded to this bit, but I'll reitterate a piece. The
scheduler already does use some of the topology macros. We (I?) don't
want to split the in-kernel topology into multiple different topology
infrastructures: one for VM, one for scheduling, one for I/O, etc. It
would be best if we could all use the same infrastructure, and just use
the information it provides for each subsystem. For example, the
scheduler could cache some of the cpu<->node mappings in local per-pool
arrays or something, rather than inventing new cpu<->pool topology.
> James Bottomley
>
>
> ------------------------------------------------------------------------
>
> # This is a BitKeeper generated patch for the following project:
> # Project Name: Linux kernel tree
> # This patch format is intended for GNU patch command version 2.5 or higher.
> # This patch includes the following deltas:
> # ChangeSet 1.934 -> 1.935
> # include/asm-i386/voyager.h 1.3 -> 1.4
> # arch/i386/Kconfig 1.16 -> 1.17
> # drivers/base/node.c 1.3 -> 1.4
> # include/asm-i386/topology.h 1.2 -> 1.3
> # include/asm-i386/numnodes.h 1.2 -> 1.3
> # arch/i386/mach-voyager/voyager_cat.c 1.7 -> 1.8
> # include/asm-i386/vic.h 1.4 -> 1.5
> # arch/i386/mach-voyager/Makefile 1.9 -> 1.10
> # drivers/base/Makefile 1.16 -> 1.17
> # (new) -> 1.1 arch/i386/mach-generic/machine_topology.h
> # (new) -> 1.1 arch/i386/mach-voyager/topology.c
> # (new) -> 1.1 arch/i386/mach-voyager/machine_topology.h
> #
> # The following is the BitKeeper ChangeSet Log
> # --------------------------------------------
> # 02/11/29 jejb@malley.(none) 1.935
> # add topology to voyager
> # --------------------------------------------
> #
> diff -Nru a/arch/i386/Kconfig b/arch/i386/Kconfig
> --- a/arch/i386/Kconfig Fri Nov 29 13:01:29 2002
> +++ b/arch/i386/Kconfig Fri Nov 29 13:01:29 2002
> @@ -1698,3 +1698,13 @@
> bool
> depends on SMP
> default y
> +
> +config BASE_NODE
> + bool
> + depends on NUMA || VOYAGER
> + default y
> +
> +config X86_NUMNODES
> + int
> + default "8" if VOYAGER
> + default "1" if !VOYAGER
Ok.. I *really* don't think that we need *another* maximum number of
nodes counter. We already have MAX_NR_NODES, and MAX_NUMNODES. The
last thing we need is one more.
> diff -Nru a/arch/i386/mach-generic/machine_topology.h b/arch/i386/mach-generic/machine_topology.h
> --- /dev/null Wed Dec 31 16:00:00 1969
> +++ b/arch/i386/mach-generic/machine_topology.h Fri Nov 29 13:01:29 2002
> @@ -0,0 +1,96 @@
> +/*
> + * linux/include/asm-i386/topology.h
> + *
> + * Written by: Matthew Dobson, IBM Corporation
> + *
> + * Copyright (C) 2002, IBM Corp.
> + *
> + * All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
> + * NON INFRINGEMENT. See the GNU General Public License for more
> + * details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + *
> + * Send feedback to <[email protected]>
> + */
> +#ifndef _MACHINE_TOPOLOGY_H
> +#define _MACHINE_TOPOLOGY_H
> +
> <snip>
> +
> +#endif
I like this. I wanted to get around to doing this anyhow. John Stultz
is doing this for summit, and I planned to follow his lead with the
sub-arch breakup. Again, we're all trying for the same thing, so one of
us should succeed.
> diff -Nru a/arch/i386/mach-voyager/Makefile b/arch/i386/mach-voyager/Makefile
> --- a/arch/i386/mach-voyager/Makefile Fri Nov 29 13:01:29 2002
> +++ b/arch/i386/mach-voyager/Makefile Fri Nov 29 13:01:29 2002
> @@ -10,7 +10,7 @@
> EXTRA_CFLAGS += -I../kernel
> export-objs :=
>
> -obj-y := setup.o voyager_basic.o voyager_thread.o
> +obj-y := setup.o voyager_basic.o voyager_thread.o topology.o
>
> obj-$(CONFIG_SMP) += voyager_smp.o voyager_cat.o
>
> diff -Nru a/arch/i386/mach-voyager/machine_topology.h b/arch/i386/mach-voyager/machine_topology.h
> --- /dev/null Wed Dec 31 16:00:00 1969
> +++ b/arch/i386/mach-voyager/machine_topology.h Fri Nov 29 13:01:29 2002
> @@ -0,0 +1,45 @@
> +/* -*- mode: c; c-basic-offset: 8 -*- */
> +
> +/* Copyright (C) 1999,2001
> + *
> + * Author: [email protected]
> + *
> + * linux/arch/i386/mach-voyager/machine_topology.h
> + */
> +#include <asm/voyager.h>
> +
> <SNIP>
> +
> +/* FIXME: these are useless defines just to get topology to compile
> + * The code needs to be NUMA cleaned up to separate node from what
> + * NUMA thinks of as a node */
> +#define __node_to_memblk(node) (node)
> +#define si_meminfo_node(i, j)
> +
If voyager has a flat memory space, I would highly recommend
#define __node_to_memblk(node) (0)
instead of (node). Returning the node number makes it look like each
node has it's own memblk with a 1-1 mapping between them. Also, your
si_meminfo_node should be able to more or less just call the non-node
version.
> diff -Nru a/arch/i386/mach-voyager/topology.c b/arch/i386/mach-voyager/topology.c
> --- /dev/null Wed Dec 31 16:00:00 1969
> +++ b/arch/i386/mach-voyager/topology.c Fri Nov 29 13:01:29 2002
> @@ -0,0 +1,51 @@
> +/* -*- mode: c; c-basic-offset: 8 -*- */
> +
> +/* Copyright (C) 2002
> + *
> + * Author: [email protected]
> + *
> + * voyager topology functions
> + */
> +
> +#include <linux/init.h>
> +#include <linux/string.h>
> +#include <asm/cpu.h>
> +#include <linux/smp.h>
> +#include <asm/topology.h>
> +
> +/* Topology mapping functions */
> +u32 voyager_node_to_cpu_mask[MAX_PROCESSOR_BOARDS] = { 0 };
> +u8 voyager_cpu_to_node[NR_CPUS] = { 0 };
> +u8 voyager_num_nodes = 0;
> +
> +struct i386_cpu cpu_devices[NR_CPUS];
> +struct i386_node node_devices[MAX_NUMNODES];
> +
> +static int __init topology_init(void)
> +{
> + int i;
> +
> + printk("VOYAGER BEGINNING TOPOLOGY INITIALISATION %d\n", MAX_NUMNODES);
> + memset(cpu_devices, 0, sizeof(cpu_devices));
> + memset(node_devices, 0, sizeof(node_devices));
> +
> + for (i = 0; i < num_online_nodes(); i++)
> + arch_register_node(i);
> + for (i = 0; i < NR_CPUS; i++)
> + if (cpu_possible(i)) arch_register_cpu(i);
> +
> + printk("NODES %d\n", num_online_nodes());
> + printk("CPU TO NODE: ");
> + for(i=0; i<NR_CPUS; i++)
> + if(cpu_possible(i))
> + printk("%d->%d ", i, voyager_cpu_to_node[i]);
> + printk("\nNODE TO CPU MASK: ");
> + for(i=0; i<voyager_num_nodes; i++)
> + printk("%d->0x%04x ", i, voyager_node_to_cpu_mask[i]);
> + printk("\n");
> +
> +
> + return 0;
> +}
> +
> +subsys_initcall(topology_init);
As I mentioned above, since you only have the one memblk, you could
easily call arch_register_memblk once, or just leave it alone like
you've done.
>
> <snip>
>
> diff -Nru a/drivers/base/Makefile b/drivers/base/Makefile
> --- a/drivers/base/Makefile Fri Nov 29 13:01:29 2002
> +++ b/drivers/base/Makefile Fri Nov 29 13:01:29 2002
> @@ -4,7 +4,8 @@
> driver.o class.o intf.o platform.o \
> cpu.o firmware.o
>
> -obj-$(CONFIG_NUMA) += node.o memblk.o
> +obj-$(CONFIG_BASE_NODE) += node.o
> +obj-$(CONFIG_NUMA) += memblk.o
>
> obj-y += fs/
>
Mentioned this above. You could leave it in and just register the
singular memblk if you liked.
> diff -Nru a/drivers/base/node.c b/drivers/base/node.c
> --- a/drivers/base/node.c Fri Nov 29 13:01:29 2002
> +++ b/drivers/base/node.c Fri Nov 29 13:01:29 2002
> @@ -93,7 +93,8 @@
>
> static int __init register_node_type(void)
> {
> + devclass_register(&node_devclass);
> driver_register(&node_driver);
> - return devclass_register(&node_devclass);
> + return 0; //devclass_register(&node_devclass);
> }
> postcore_initcall(register_node_type);
I've submitted this fix separtately. It really needs to go in the
mainline, without this NUMA boxen panic.
> diff -Nru a/include/asm-i386/numnodes.h b/include/asm-i386/numnodes.h
> --- a/include/asm-i386/numnodes.h Fri Nov 29 13:01:29 2002
> +++ b/include/asm-i386/numnodes.h Fri Nov 29 13:01:29 2002
> @@ -6,7 +6,7 @@
> #ifdef CONFIG_X86_NUMAQ
> #include <asm/numaq.h>
> #else
> -#define MAX_NUMNODES 1
> +#define MAX_NUMNODES CONFIG_X86_NUMNODES
> #endif /* CONFIG_X86_NUMAQ */
>
> #endif /* _ASM_MAX_NUMNODES_H */
I'd like to see some of the confusion with MAX_NR_NODES and MAX_NUMNODES
disappear, but apparently no one liked my patch. I'll dust it off and
resubmit it. I really think it'd be beneficial to only have one
variable for this. I also suppose that there's no reason this has to be
X86 specific. We could have this for most arch's and just default to 1.
>
><snip>
>
> diff -Nru a/include/asm-i386/vic.h b/include/asm-i386/vic.h
> --- a/include/asm-i386/vic.h Fri Nov 29 13:01:29 2002
> +++ b/include/asm-i386/vic.h Fri Nov 29 13:01:29 2002
> @@ -3,6 +3,8 @@
> * Author: [email protected]
> *
> * Standard include definitions for the NCR Voyager Interrupt Controller */
> +#ifndef _ASM_VIC_H
> +#define _ASM_VIC_H
>
> /* The eight CPI vectors. To activate a CPI, you write a bit mask
> * corresponding to the processor set to be interrupted into the
> @@ -59,3 +61,5 @@
> #define VIC_BOOT_INTERRUPT_MASK 0xfe
>
> extern void smp_vic_timer_interrupt(struct pt_regs *regs);
> +
> +#endif
> diff -Nru a/include/asm-i386/voyager.h b/include/asm-i386/voyager.h
> --- a/include/asm-i386/voyager.h Fri Nov 29 13:01:29 2002
> +++ b/include/asm-i386/voyager.h Fri Nov 29 13:01:29 2002
> @@ -3,6 +3,8 @@
> * Author: [email protected]
> *
> * Standard include definitions for the NCR Voyager system */
> +#ifndef _ASM_VOYAGER_H_
> +#define _ASM_VOYAGER_H_
>
> #undef VOYAGER_DEBUG
> #undef VOYAGER_CAT_DEBUG
> @@ -519,3 +521,5 @@
> #define VOYAGER_PSI_SUBREAD 2
> #define VOYAGER_PSI_SUBWRITE 3
> extern void voyager_cat_psi(__u8, __u16, __u8 *);
> +
> +#endif
This is voyager specific and I'm sure it's fine.
I'll have a go at a counter-patch tomorrow... ;)
Cheers!
-Matt