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Re: [Qemu-devel] [PATCH] numa, spapr: align default numa node memory siz
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH] numa, spapr: align default numa node memory size to 256MB |
Date: |
Mon, 20 Mar 2017 11:30:42 +0000 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
On Mon, Mar 20, 2017 at 12:24:26PM +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).
That commit only enabled the feature for the pseries-2.5 machine type
several releases back now...
> 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>
> ---
> dtc | 2 +-
> numa.c | 14 +++++++++-----
> 2 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/dtc b/dtc
> index 558cd81..fa8bc7f 160000
> --- a/dtc
> +++ b/dtc
> @@ -1 +1 @@
> -Subproject commit 558cd81bdd432769b59bff01240c44f82cfb1a9d
> +Subproject commit fa8bc7f928ac25f23532afc8beb2073efc8fb063
This looks unrelated
> diff --git a/numa.c b/numa.c
> index e01cb54..a911284 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -337,15 +337,19 @@ 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,
> - * the final node gets the rest.
> - */
> +#if defined(TARGET_PPC64)
> + /* pseries requests each node's border has to be 256 MB aligned
> */
> + const uint64_t numa_mem_align_mask = ~((1 << 28UL) - 1);
> +#else
but here you're forcing 256 MB alignement for all machine types. This is
surely breaking machine ABI compat for anyone who previously used -numa
with QEMU and upgrades to new QEMU expecting the same ABI.
Regards,
Daniel
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