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Re: [Qemu-ppc] [PATCH v2] numa, spapr: align default numa node memory si
From: |
David Gibson |
Subject: |
Re: [Qemu-ppc] [PATCH v2] numa, spapr: align default numa node memory size to 256MB |
Date: |
Tue, 21 Mar 2017 12:03:21 +1100 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Mon, Mar 20, 2017 at 04:11:14PM -0300, Eduardo Habkost wrote:
> On Mon, Mar 20, 2017 at 03:12:44PM +0100, Laurent Vivier wrote:
> > Since commit 224245b ("spapr: Add LMB DR connectors"), NUMA node
> > memory size must be aligned to 256MB (SPAPR_MEMORY_BLOCK_SIZE).
> >
> > But when "-numa" option is provided without "mem" parameter,
> > the memory is equally divided between nodes, but 8MB aligned.
> > This can be not valid for pseries.
> >
> > In that case we can have:
> > $ ./ppc64-softmmu/qemu-system-ppc64 -m 4G -numa node -numa node -numa node
> > qemu-system-ppc64: Node 0 memory size 0x55000000 is not aligned to 256 MiB
> >
> > With this patch, we have:
> > (qemu) info numa
> > 3 nodes
> > node 0 cpus: 0
> > node 0 size: 1280 MB
> > node 1 cpus:
> > node 1 size: 1280 MB
> > node 2 cpus:
> > node 2 size: 1536 MB
> >
> > Signed-off-by: Laurent Vivier <address@hidden>
In agree with Eduardo's suggested comment changes. Apart from that,
Reviewed-by: David Gibson <address@hidden>
Eduardo, do you want to take the final spin through your tree, or
should I take it through mine?
>
> The code looks good, but a few comments explaining the reason for
> the numa_mem_align_shift values would be interesting. Additional
> comments below:
>
> > ---
> > v2:
> > - remove dtc
> > - Add a field in MachineClass to only modify the
> > numa node memory alignment value for pseries-2.9
> > and upper.
> >
> > hw/core/machine.c | 3 +++
> > hw/ppc/spapr.c | 2 ++
> > include/hw/boards.h | 1 +
> > numa.c | 4 ++--
> > 4 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > index 0d92672..2ad5ab5 100644
> > --- a/hw/core/machine.c
> > +++ b/hw/core/machine.c
> > @@ -396,6 +396,9 @@ static void machine_class_init(ObjectClass *oc, void
> > *data)
> > mc->default_ram_size = 128 * M_BYTE;
> > mc->rom_file_has_mr = true;
> >
> > + /* numa node memory size aligned on 8MB by default */
> > + mc->numa_mem_align_shift = 23;
> > +
>
> This could include the original "On Linux, each node's border has
> to be 8MB aligned" comment from parse_numa_opts(), to explain the
> reason for the 8MB default.
>
> > object_class_property_add_str(oc, "accel",
> > machine_get_accel, machine_set_accel, &error_abort);
> > object_class_property_set_description(oc, "accel",
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 6ee566d..1e72fe8 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -3096,6 +3096,7 @@ static void spapr_machine_class_init(ObjectClass *oc,
> > void *data)
> > xic->ics_resend = spapr_ics_resend;
> > xic->icp_get = spapr_icp_get;
> > ispc->print_info = spapr_pic_print_info;
> > + mc->numa_mem_align_shift = 28;
>
> A comment explaining why spapr requires 256MB alignment would be
> nice.
>
> > }
> >
> > static const TypeInfo spapr_machine_info = {
> > @@ -3180,6 +3181,7 @@ static void
> > spapr_machine_2_8_class_options(MachineClass *mc)
> > {
> > spapr_machine_2_9_class_options(mc);
> > SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_8);
> > + mc->numa_mem_align_shift = 23;
> > }
> >
> > DEFINE_SPAPR_MACHINE(2_8, "2.8", false);
> > diff --git a/include/hw/boards.h b/include/hw/boards.h
> > index 269d0ba..31d9c72 100644
> > --- a/include/hw/boards.h
> > +++ b/include/hw/boards.h
> > @@ -135,6 +135,7 @@ struct MachineClass {
> > bool rom_file_has_mr;
> > int minimum_page_bits;
> > bool has_hotpluggable_cpus;
> > + int numa_mem_align_shift;
> >
> > HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
> > DeviceState *dev);
> > diff --git a/numa.c b/numa.c
> > index e01cb54..98e4d02 100644
> > --- a/numa.c
> > +++ b/numa.c
> > @@ -338,12 +338,12 @@ void parse_numa_opts(MachineClass *mc)
> > if (i == nb_numa_nodes) {
> > uint64_t usedmem = 0;
> >
> > - /* On Linux, each node's border has to be 8MB aligned,
> > + /* On Linux, each node's border has to be aligned,
> > * the final node gets the rest.
> > */
>
> I assume that the 256MB alignment in spapr is not just because of
> Linux (is it?). This makes the comment misleading.
>
> I would rewrite it to something like: "Align each node according
> to the alignment requirements of the machine class".
>
>
> > for (i = 0; i < nb_numa_nodes - 1; i++) {
> > numa_info[i].node_mem = (ram_size / nb_numa_nodes) &
> > - ~((1 << 23UL) - 1);
> > + ~((1 << mc->numa_mem_align_shift)
> > - 1);
> > usedmem += numa_info[i].node_mem;
> > }
> > numa_info[i].node_mem = ram_size - usedmem;
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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