Commit 57924bcd authored by Igor Mammedov's avatar Igor Mammedov Committed by Eduardo Habkost
Browse files

numa: introduce machine callback for VCPU to node mapping 



Current default round-robin way of distributing VCPUs among
NUMA nodes might be wrong in case on multi-core/threads
CPUs. Making guests confused wrt topology where cores from
the same socket are on different nodes.

Allow a machine to override default mapping by providing
 MachineClass::cpu_index_to_socket_id()
callback which would allow it group VCPUs from a socket
on the same NUMA node.

Signed-off-by: default avatarIgor Mammedov <imammedo@redhat.com>
Reviewed-by: default avatarAndreas Färber <afaerber@suse.de>
Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
parent 3ef71975

include/hw/boards.h

+5 −0
Original line number Diff line number Diff line
@@ -82,6 +82,10 @@ bool machine_mem_merge(MachineState *machine); 
 *    of HotplugHandler object, which handles hotplug operation

 *    for a given @dev. It may return NULL if @dev doesn't require

 *    any actions to be performed by hotplug handler.

 * @cpu_index_to_socket_id:

 *    used to provide @cpu_index to socket number mapping, allowing

 *    a machine to group CPU threads belonging to the same socket/package

 *    Returns: socket number given cpu_index belongs to.

 */

struct MachineClass {

    /*< private >*/
@@ -118,6 +122,7 @@ struct MachineClass { 


    HotplugHandler *(*get_hotplug_handler)(MachineState *machine,

                                           DeviceState *dev);

    unsigned (*cpu_index_to_socket_id)(unsigned cpu_index);

};



/**

include/sysemu/numa.h

+2 −1
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include "qemu/option.h"

#include "sysemu/sysemu.h"

#include "sysemu/hostmem.h"

#include "hw/boards.h"



extern int nb_numa_nodes;   /* Number of NUMA nodes */
@@ -16,7 +17,7 @@ typedef struct node_info { 
    bool present;

} NodeInfo;

extern NodeInfo numa_info[MAX_NODES];

void parse_numa_opts(void);

void parse_numa_opts(MachineClass *mc);

void numa_post_machine_init(void);

void query_numa_node_mem(uint64_t node_mem[]);

extern QemuOptsList qemu_numa_opts;

numa.c

+13 −5
Original line number Diff line number Diff line
@@ -202,7 +202,7 @@ static void validate_numa_cpus(void) 
    }

}



void parse_numa_opts(void)

void parse_numa_opts(MachineClass *mc)

{

    int i;
@@ -270,13 +270,21 @@ void parse_numa_opts(void) 
                break;

            }

        }

        /* assigning the VCPUs round-robin is easier to implement, guest OSes

         * must cope with this anyway, because there are BIOSes out there in

         * real machines which also use this scheme.

        /* Historically VCPUs were assigned in round-robin order to NUMA

         * nodes. However it causes issues with guest not handling it nice

         * in case where cores/threads from a multicore CPU appear on

         * different nodes. So allow boards to override default distribution

         * rule grouping VCPUs by socket so that VCPUs from the same socket

         * would be on the same node.

         */

        if (i == nb_numa_nodes) {

            for (i = 0; i < max_cpus; i++) {

                set_bit(i, numa_info[i % nb_numa_nodes].node_cpu);

                unsigned node_id = i % nb_numa_nodes;

                if (mc->cpu_index_to_socket_id) {

                    node_id = mc->cpu_index_to_socket_id(i) % nb_numa_nodes;

                }



                set_bit(i, numa_info[node_id].node_cpu);

            }

        }

vl.c

+1 −1
Original line number Diff line number Diff line
@@ -4170,7 +4170,7 @@ int main(int argc, char **argv, char **envp) 
    default_drive(default_floppy, snapshot, IF_FLOPPY, 0, FD_OPTS);

    default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);



    parse_numa_opts();

    parse_numa_opts(machine_class);



    if (qemu_opts_foreach(qemu_find_opts("mon"), mon_init_func, NULL, 1) != 0) {

        exit(1);