From 3bfe57165b4bf86a431099078df422f54598f5c6 Mon Sep 17 00:00:00 2001 From: Laurent Vivier Date: Tue, 2 May 2017 18:29:55 +0200 Subject: numa: equally distribute memory on nodes When there are more nodes than available memory to put the minimum allowed memory by node, all the memory is put on the last node. This is because we put (ram_size / nb_numa_nodes) & ~((1 << mc->numa_mem_align_shift) - 1); on each node, and in this case the value is 0. This is particularly true with pseries, as the memory must be aligned to 256MB. To avoid this problem, this patch uses an error diffusion algorithm [1] to distribute equally the memory on nodes. We introduce numa_auto_assign_ram() function in MachineClass to keep compatibility between machine type versions. The legacy function is used with pseries-2.9, pc-q35-2.9 and pc-i440fx-2.9 (and previous), the new one with all others. Example: qemu-system-ppc64 -S -nographic -nodefaults -monitor stdio -m 1G -smp 8 \ -numa node -numa node -numa node \ -numa node -numa node -numa node Before: (qemu) info numa 6 nodes node 0 cpus: 0 6 node 0 size: 0 MB node 1 cpus: 1 7 node 1 size: 0 MB node 2 cpus: 2 node 2 size: 0 MB node 3 cpus: 3 node 3 size: 0 MB node 4 cpus: 4 node 4 size: 0 MB node 5 cpus: 5 node 5 size: 1024 MB After: (qemu) info numa 6 nodes node 0 cpus: 0 6 node 0 size: 0 MB node 1 cpus: 1 7 node 1 size: 256 MB node 2 cpus: 2 node 2 size: 0 MB node 3 cpus: 3 node 3 size: 256 MB node 4 cpus: 4 node 4 size: 256 MB node 5 cpus: 5 node 5 size: 256 MB [1] https://en.wikipedia.org/wiki/Error_diffusion Signed-off-by: Laurent Vivier Message-Id: <20170502162955.1610-2-lvivier@redhat.com> Reviewed-by: Eduardo Habkost [ehabkost: s/ram_size/size/ at numa_default_auto_assign_ram()] Signed-off-by: Eduardo Habkost --- include/hw/boards.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/hw/boards.h') diff --git a/include/hw/boards.h b/include/hw/boards.h index 31d9c72fb0..99458eb859 100644 --- a/include/hw/boards.h +++ b/include/hw/boards.h @@ -136,6 +136,8 @@ struct MachineClass { int minimum_page_bits; bool has_hotpluggable_cpus; int numa_mem_align_shift; + void (*numa_auto_assign_ram)(MachineClass *mc, NodeInfo *nodes, + int nb_nodes, ram_addr_t size); HotplugHandler *(*get_hotplug_handler)(MachineState *machine, DeviceState *dev); -- cgit 1.4.1