Re: [Qemu-devel] [PATCH v3 3/3] memory: drop some wrappers that waste cpu cycle

[Fam Zheng <famz@redhat.com>]

On Thu, 05/12 18:07, Gonglei wrote:
> For better performance, we can use RAMblock
> directly stored in memory_region at present.
> 
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>
> ---
>  exec.c                  | 33 ++-------------------------------
>  hw/misc/ivshmem.c       |  8 +++++---
>  hw/virtio/vhost-user.c  | 13 ++++++++-----
>  include/exec/ram_addr.h |  4 +---
>  memory.c                |  2 +-
>  5 files changed, 17 insertions(+), 43 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 117c9a8..f8de928 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1812,38 +1812,9 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
>  }
>  #endif /* !_WIN32 */
>  
> -int qemu_get_ram_fd(ram_addr_t addr)
> +void *qemu_get_ram_block_host_ptr(RAMBlock *ram_block)
>  {
> -    RAMBlock *block;
> -    int fd;
> -
> -    rcu_read_lock();
> -    block = qemu_get_ram_block(addr);
> -    fd = block->fd;
> -    rcu_read_unlock();
> -    return fd;
> -}
> -
> -void qemu_set_ram_fd(ram_addr_t addr, int fd)
> -{
> -    RAMBlock *block;
> -
> -    rcu_read_lock();
> -    block = qemu_get_ram_block(addr);
> -    block->fd = fd;
> -    rcu_read_unlock();
> -}
> -
> -void *qemu_get_ram_block_host_ptr(ram_addr_t addr)
> -{
> -    RAMBlock *block;
> -    void *ptr;
> -
> -    rcu_read_lock();
> -    block = qemu_get_ram_block(addr);
> -    ptr = ramblock_ptr(block, 0);
> -    rcu_read_unlock();
> -    return ptr;
> +    return ramblock_ptr(ram_block, 0);
>  }
>  
>  /* Return a host pointer to ram allocated with qemu_ram_alloc.
> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> index e40f23b..1e930fa 100644
> --- a/hw/misc/ivshmem.c
> +++ b/hw/misc/ivshmem.c
> @@ -533,7 +533,9 @@ static void process_msg_shmem(IVShmemState *s, int fd, Error **errp)
>      }
>      memory_region_init_ram_ptr(&s->server_bar2, OBJECT(s),
>                                 "ivshmem.bar2", size, ptr);
> -    qemu_set_ram_fd(memory_region_get_ram_addr(&s->server_bar2), fd);
> +    assert(s->server_bar2.ram_block);
> +    s->server_bar2.ram_block->fd = fd;
> +
>      s->ivshmem_bar2 = &s->server_bar2;
>  }
>  
> @@ -939,8 +941,8 @@ static void ivshmem_exit(PCIDevice *dev)
>                  error_report("Failed to munmap shared memory %s",
>                               strerror(errno));
>              }
> -
> -            fd = qemu_get_ram_fd(memory_region_get_ram_addr(s->ivshmem_bar2));

Maybe this is okay but personally I think it is cleaner to add a
qemu_{set,get}_ramblock_fd pair.

Fam