From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46708) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d3Jqm-0003aw-Vx for qemu-devel@nongnu.org; Wed, 26 Apr 2017 06:07:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d3Jqj-00024g-Ro for qemu-devel@nongnu.org; Wed, 26 Apr 2017 06:07:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38806) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d3Jqj-00024B-LQ for qemu-devel@nongnu.org; Wed, 26 Apr 2017 06:07:05 -0400 From: Laurent Vivier Date: Wed, 26 Apr 2017 12:07:01 +0200 Message-Id: <20170426100701.21893-1-lvivier@redhat.com> Subject: [Qemu-devel] [PATCH] numa: equally distribute memory on nodes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: David Gibson , Thomas Huth , qemu-devel@nongnu.org, Laurent Vivier When there is more nodes than memory available 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. 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 --- numa.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/numa.c b/numa.c index 6fc2393..bcf1c54 100644 --- a/numa.c +++ b/numa.c @@ -336,15 +336,19 @@ void parse_numa_opts(MachineClass *mc) } } if (i == nb_numa_nodes) { - uint64_t usedmem = 0; + uint64_t usedmem = 0, node_mem; + uint64_t granularity = ram_size / nb_numa_nodes; + uint64_t propagate = 0; /* 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) & + node_mem = (granularity + propagate) & ~((1 << mc->numa_mem_align_shift) - 1); - usedmem += numa_info[i].node_mem; + propagate = granularity + propagate - node_mem; + numa_info[i].node_mem = node_mem; + usedmem += node_mem; } numa_info[i].node_mem = ram_size - usedmem; } -- 2.9.3