Re: [Qemu-devel] [PATCH 3/3] memory: pass RAMBlock as a agrument

[Fam Zheng <famz@redhat.com>]

On Wed, 04/20 11:34, Gonglei wrote:
> In this way, we can avoid to invoke qemu_get_ram_block()
> at most time, which can save cpu cycle.
> 
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>
> ---
>  exec.c                  | 48 ++++++++++++++++++++++++++++++------------------
>  hw/misc/ivshmem.c       |  6 ++++--
>  hw/virtio/vhost-user.c  | 11 ++++++-----
>  include/exec/ram_addr.h |  6 +++---
>  memory.c                |  3 ++-
>  5 files changed, 45 insertions(+), 29 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index b0ecbcd..f3348aa 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1813,37 +1813,49 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
>  }
>  #endif /* !_WIN32 */
>  
> -int qemu_get_ram_fd(ram_addr_t addr)
> +int qemu_get_ram_fd(RAMBlock *ram_block, ram_addr_t addr)
>  {
> -    RAMBlock *block;
> +    RAMBlock *block = ram_block;
>      int fd;
>  
> -    rcu_read_lock();
> -    block = qemu_get_ram_block(addr);
> -    fd = block->fd;
> -    rcu_read_unlock();
> +    if (block == NULL) {

Is this branch even used? It seems no caller passes in literal NULL in this
patch. Can the variables be NULL?

If not, I think we can simply drop addr.

> +        rcu_read_lock();
> +        block = qemu_get_ram_block(addr);
> +        fd = block->fd;
> +        rcu_read_unlock();
> +    } else {
> +        fd = block->fd;
> +    }
>      return fd;
>  }
>  
> -void qemu_set_ram_fd(ram_addr_t addr, int fd)
> +void qemu_set_ram_fd(RAMBlock *ram_block, ram_addr_t addr, int fd)
>  {
> -    RAMBlock *block;
> +    RAMBlock *block = ram_block;
>  
> -    rcu_read_lock();
> -    block = qemu_get_ram_block(addr);
> -    block->fd = fd;
> -    rcu_read_unlock();
> +    if (block == NULL) {

Same here...

> +        rcu_read_lock();
> +        block = qemu_get_ram_block(addr);
> +        block->fd = fd;
> +        rcu_read_unlock();
> +    } else {
> +        block->fd = fd;
> +    }
>  }
>  
> -void *qemu_get_ram_block_host_ptr(ram_addr_t addr)
> +void *qemu_get_ram_block_host_ptr(RAMBlock *ram_block, ram_addr_t addr)
>  {
> -    RAMBlock *block;
> +    RAMBlock *block = ram_block;
>      void *ptr;
>  
> -    rcu_read_lock();
> -    block = qemu_get_ram_block(addr);
> -    ptr = ramblock_ptr(block, 0);
> -    rcu_read_unlock();
> +    if (block == NULL) {

And here.

> +        rcu_read_lock();
> +        block = qemu_get_ram_block(addr);
> +        ptr = ramblock_ptr(block, 0);
> +        rcu_read_unlock();
> +    } else {
> +        ptr = ramblock_ptr(block, 0);
> +    }
>      return ptr;
>  }
>  
> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> index e40f23b..5ba0af7 100644
> --- a/hw/misc/ivshmem.c
> +++ b/hw/misc/ivshmem.c
> @@ -533,7 +533,8 @@ 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);
> +    qemu_set_ram_fd(s->server_bar2.ram_block,
> +                    memory_region_get_ram_addr(&s->server_bar2), fd);
>      s->ivshmem_bar2 = &s->server_bar2;
>  }
>  
> @@ -940,7 +941,8 @@ static void ivshmem_exit(PCIDevice *dev)
>                               strerror(errno));
>              }
>  
> -            fd = qemu_get_ram_fd(memory_region_get_ram_addr(s->ivshmem_bar2));
> +            fd = qemu_get_ram_fd(s->ivshmem_bar2->ram_block,
> +                                 memory_region_get_ram_addr(s->ivshmem_bar2));
>              close(fd);
>          }
>  
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 5914e85..4b93533 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -248,17 +248,18 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev,
>      for (i = 0; i < dev->mem->nregions; ++i) {
>          struct vhost_memory_region *reg = dev->mem->regions + i;
>          ram_addr_t ram_addr;
> +        MemoryRegion *mr;
>  
>          assert((uintptr_t)reg->userspace_addr == reg->userspace_addr);
> -        qemu_ram_addr_from_host((void *)(uintptr_t)reg->userspace_addr,
> +        mr = qemu_ram_addr_from_host((void *)(uintptr_t)reg->userspace_addr,
>                                  &ram_addr);
> -        fd = qemu_get_ram_fd(ram_addr);
> +        fd = qemu_get_ram_fd(mr->ram_block, ram_addr);
>          if (fd > 0) {
>              msg.payload.memory.regions[fd_num].userspace_addr = reg->userspace_addr;
>              msg.payload.memory.regions[fd_num].memory_size  = reg->memory_size;
>              msg.payload.memory.regions[fd_num].guest_phys_addr = reg->guest_phys_addr;
>              msg.payload.memory.regions[fd_num].mmap_offset = reg->userspace_addr -
> -                (uintptr_t) qemu_get_ram_block_host_ptr(ram_addr);
> +                (uintptr_t) qemu_get_ram_block_host_ptr(mr->ram_block, ram_addr);
>              assert(fd_num < VHOST_MEMORY_MAX_NREGIONS);
>              fds[fd_num++] = fd;
>          }
> @@ -622,11 +623,11 @@ static bool vhost_user_can_merge(struct vhost_dev *dev,
>  
>      mr = qemu_ram_addr_from_host((void *)(uintptr_t)start1, &ram_addr);
>      assert(mr);
> -    mfd = qemu_get_ram_fd(ram_addr);
> +    mfd = qemu_get_ram_fd(mr->ram_block, ram_addr);
>  
>      mr = qemu_ram_addr_from_host((void *)(uintptr_t)start2, &ram_addr);
>      assert(mr);
> -    rfd = qemu_get_ram_fd(ram_addr);
> +    rfd = qemu_get_ram_fd(mr->ram_block, ram_addr);
>  
>      return mfd == rfd;
>  }
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 5b6e1b8..4e1e5c3 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -105,9 +105,9 @@ RAMBlock *qemu_ram_alloc_resizeable(ram_addr_t size, ram_addr_t max_size,
>                                                      uint64_t length,
>                                                      void *host),
>                                      MemoryRegion *mr, Error **errp);
> -int qemu_get_ram_fd(ram_addr_t addr);
> -void qemu_set_ram_fd(ram_addr_t addr, int fd);
> -void *qemu_get_ram_block_host_ptr(ram_addr_t addr);
> +int qemu_get_ram_fd(RAMBlock *ram_block, ram_addr_t addr);
> +void qemu_set_ram_fd(RAMBlock *ram_block, ram_addr_t addr, int fd);
> +void *qemu_get_ram_block_host_ptr(RAMBlock *ram_block, ram_addr_t addr);
>  void qemu_ram_free(RAMBlock *block);
>  
>  int qemu_ram_resize(RAMBlock *block, ram_addr_t newsize, Error **errp);
> diff --git a/memory.c b/memory.c
> index 239e6da..fa2b6e2 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1641,7 +1641,8 @@ int memory_region_get_fd(MemoryRegion *mr)
>  
>      assert(mr->ram_block);
>  
> -    return qemu_get_ram_fd(memory_region_get_ram_addr(mr) & TARGET_PAGE_MASK);
> +    return qemu_get_ram_fd(mr->ram_block,
> +                      memory_region_get_ram_addr(mr) & TARGET_PAGE_MASK);
>  }
>  
>  void *memory_region_get_ram_ptr(MemoryRegion *mr)
> -- 
> 1.7.12.4
> 
>