[dpdk-dev] [PATCH v2] eal: change default per socket memory allocation

[David Marchand <david.marchand@6wind.com>]

From: Didier Pallard <didier.pallard@6wind.com>

Currently, if there is more memory in hugepages than the amount
requested by dpdk application, the memory is allocated by taking as much
memory as possible from each socket, starting from first one.
For example if a system is configured with 8 GB in 2 sockets (4 GB per
socket), and dpdk is requesting only 4GB of memory, all memory will be
taken in socket 0 (that have exactly 4GB of free hugepages) even if some
cores are configured on socket 1, and there are free hugepages on socket
1...

Change this behaviour to allocate memory on all sockets where some cores
are configured, spreading the memory amongst sockets using following
ratio per socket:
N° of cores configured on the socket / Total number of configured cores
* requested memory

This algorithm is used when memory amount is specified globally using
-m option. Per socket memory allocation can always be done using
--socket-mem option.

Changes included in v2:
- only update linux implementation as bsd looks not to be ready for numa
- if new algorithm fails, then defaults to previous behaviour

Signed-off-by: Didier Pallard <didier.pallard@6wind.com>
Signed-off-by: David Marchand <david.marchand@6wind.com>
---
 lib/librte_eal/linuxapp/eal/eal_memory.c |   50 +++++++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 5 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
index 73a6394..471dcfd 100644
--- a/lib/librte_eal/linuxapp/eal/eal_memory.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
@@ -881,13 +881,53 @@ calc_num_pages_per_socket(uint64_t * memory,
 	if (num_hp_info == 0)
 		return -1;
 
-	for (socket = 0; socket < RTE_MAX_NUMA_NODES && total_mem != 0; socket++) {
-		/* if specific memory amounts per socket weren't requested */
-		if (internal_config.force_sockets == 0) {
+	/* if specific memory amounts per socket weren't requested */
+	if (internal_config.force_sockets == 0) {
+		int cpu_per_socket[RTE_MAX_NUMA_NODES];
+		size_t default_size, total_size;
+		unsigned lcore_id;
+
+		/* Compute number of cores per socket */
+		memset(cpu_per_socket, 0, sizeof(cpu_per_socket));
+		RTE_LCORE_FOREACH(lcore_id) {
+			cpu_per_socket[rte_lcore_to_socket_id(lcore_id)]++;
+		}
+
+		/*
+		 * Automatically spread requested memory amongst detected sockets according
+		 * to number of cores from cpu mask present on each socket
+		 */
+		total_size = internal_config.memory;
+		for (socket = 0; socket < RTE_MAX_NUMA_NODES && total_size != 0; socket++) {
+
+			/* Set memory amount per socket */
+			default_size = (internal_config.memory * cpu_per_socket[socket])
+			                / rte_lcore_count();
+
+			/* Limit to maximum available memory on socket */
+			default_size = RTE_MIN(default_size, get_socket_mem_size(socket));
+
+			/* Update sizes */
+			memory[socket] = default_size;
+			total_size -= default_size;
+		}
+
+		/*
+		 * If some memory is remaining, try to allocate it by getting all 
+		 * available memory from sockets, one after the other
+		 */
+		for (socket = 0; socket < RTE_MAX_NUMA_NODES && total_size != 0; socket++) {
 			/* take whatever is available */
-			memory[socket] = RTE_MIN(get_socket_mem_size(socket),
-					total_mem);
+			default_size = RTE_MIN(get_socket_mem_size(socket) - memory[socket],
+			                       total_size);
+
+			/* Update sizes */
+			memory[socket] += default_size;
+			total_size -= default_size;
 		}
+	}
+
+	for (socket = 0; socket < RTE_MAX_NUMA_NODES && total_mem != 0; socket++) {
 		/* skips if the memory on specific socket wasn't requested */
 		for (i = 0; i < num_hp_info && memory[socket] != 0; i++){
 			hp_used[i].hugedir = hp_info[i].hugedir;
-- 
1.7.10.4