Commit 612263cf authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

memory: avoid unnecessary object_ref/unref 



For the common case of DMA into non-hotplugged RAM, it is unnecessary
but expensive to do object_ref/unref.  Add back an owner field to
MemoryRegion, so that these memory regions can skip the reference
counting.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a676854f

include/exec/memory.h

+1 −0
Original line number Diff line number Diff line
@@ -172,6 +172,7 @@ struct MemoryRegion { 
    bool global_locking;

    uint8_t dirty_log_mask;

    ram_addr_t ram_addr;

    Object *owner;

    const MemoryRegionIOMMUOps *iommu_ops;



    const MemoryRegionOps *ops;

memory.c

+12 −16
Original line number Diff line number Diff line
@@ -905,20 +905,22 @@ void memory_region_init(MemoryRegion *mr, 
                        const char *name,

                        uint64_t size)

{

    if (!owner) {

        owner = container_get(qdev_get_machine(), "/unattached");

    }



    object_initialize(mr, sizeof(*mr), TYPE_MEMORY_REGION);

    mr->size = int128_make64(size);

    if (size == UINT64_MAX) {

        mr->size = int128_2_64();

    }

    mr->name = g_strdup(name);

    mr->owner = owner;



    if (name) {

        char *escaped_name = memory_region_escape_name(name);

        char *name_array = g_strdup_printf("%s[*]", escaped_name);



        if (!owner) {

            owner = container_get(qdev_get_machine(), "/unattached");

        }



        object_property_add_child(owner, name_array, OBJECT(mr), &error_abort);

        object_unref(OBJECT(mr));

        g_free(name_array);
@@ -1369,24 +1371,18 @@ void memory_region_ref(MemoryRegion *mr) 
     * The memory region is a child of its owner.  As long as the

     * owner doesn't call unparent itself on the memory region,

     * ref-ing the owner will also keep the memory region alive.

     * Memory regions without an owner are supposed to never go away,

     * but we still ref/unref them for debugging purposes.

     * Memory regions without an owner are supposed to never go away;

     * we do not ref/unref them because it slows down DMA sensibly.

     */

    Object *obj = OBJECT(mr);

    if (obj && obj->parent) {

        object_ref(obj->parent);

    } else {

        object_ref(obj);

    if (mr && mr->owner) {

        object_ref(mr->owner);

    }

}



void memory_region_unref(MemoryRegion *mr)

{

    Object *obj = OBJECT(mr);

    if (obj && obj->parent) {

        object_unref(obj->parent);

    } else {

        object_unref(obj);

    if (mr && mr->owner) {

        object_unref(mr->owner);

    }

}