Re: [Qemu-devel] [PATCH v4 20/29] hostmem: allow preallocation of any memory region

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 9 Jun 2014 18:25:25 +0800
Hu Tao <hutao@cn.fujitsu.com> wrote:

> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> And allow preallocation of file-based memory even without -mem-prealloc.
> Some care is necessary because -mem-prealloc does not allow disabling
> preallocation for hostmem-file.
maybe 'prealloc' property should belong to hostmem-file instead of the
abstract hostmem.

> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> ---
>  backends/hostmem-file.c  |  3 +++
>  backends/hostmem.c       | 42 ++++++++++++++++++++++++++++++++++++++++++
>  exec.c                   |  7 +++++++
>  include/exec/memory.h    | 10 ++++++++++
>  include/exec/ram_addr.h  |  1 +
>  include/sysemu/hostmem.h |  1 +
>  memory.c                 | 11 +++++++++++
>  7 files changed, 75 insertions(+)
> 
[...]

> @@ -165,6 +204,9 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
>          if (!backend->dump) {
>              qemu_madvise(ptr, sz, QEMU_MADV_DONTDUMP);
>          }
> +        if (backend->prealloc) {
> +            os_mem_prealloc(memory_region_get_fd(&backend->mr), ptr, sz);
> +        }
could it be done inside of hostmem_file->alloc()?

>      }
>  }
>  
> diff --git a/exec.c b/exec.c
> index 739f0cf..520d673 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1432,6 +1432,13 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
>  }
>  #endif /* !_WIN32 */
>  
> +int qemu_get_ram_fd(ram_addr_t addr)
> +{
> +    RAMBlock *block = qemu_get_ram_block(addr);
> +
> +    return block->fd;
> +}
> +
>  /* Return a host pointer to ram allocated with qemu_ram_alloc.
>     With the exception of the softmmu code in this file, this should
>     only be used for local memory (e.g. video ram) that the device owns,
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 82d7781..36226f7 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -534,6 +534,16 @@ bool memory_region_is_logging(MemoryRegion *mr);
>  bool memory_region_is_rom(MemoryRegion *mr);
>  
>  /**
> + * memory_region_get_fd: Get a file descriptor backing a RAM memory region.
> + *
> + * Returns a file descriptor backing a file-based RAM memory region,
> + * or -1 if the region is not a file-based RAM memory region.
> + *
> + * @mr: the RAM or alias memory region being queried.
> + */
> +int memory_region_get_fd(MemoryRegion *mr);
> +
> +/**
>   * memory_region_get_ram_ptr: Get a pointer into a RAM memory region.
>   *
>   * Returns a host pointer to a RAM memory region (created with
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index f9518a6..d352f60 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -27,6 +27,7 @@ ram_addr_t qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
>  ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
>                                     MemoryRegion *mr);
>  ram_addr_t qemu_ram_alloc(ram_addr_t size, MemoryRegion *mr);
> +int qemu_get_ram_fd(ram_addr_t addr);
>  void *qemu_get_ram_ptr(ram_addr_t addr);
>  void qemu_ram_free(ram_addr_t addr);
>  void qemu_ram_free_from_ptr(ram_addr_t addr);
> diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
> index ede5ec9..4cae673 100644
> --- a/include/sysemu/hostmem.h
> +++ b/include/sysemu/hostmem.h
> @@ -53,6 +53,7 @@ struct HostMemoryBackend {
>      /* protected */
>      uint64_t size;
>      bool merge, dump;
> +    bool prealloc, force_prealloc;
>  
>      MemoryRegion mr;
>  };
> diff --git a/memory.c b/memory.c
> index 310729a..bcef72b 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1258,6 +1258,17 @@ void memory_region_reset_dirty(MemoryRegion *mr, hwaddr addr,
>      cpu_physical_memory_reset_dirty(mr->ram_addr + addr, size, client);
>  }
>  
> +int memory_region_get_fd(MemoryRegion *mr)
> +{
> +    if (mr->alias) {
> +        return memory_region_get_fd(mr->alias);
> +    }
> +
> +    assert(mr->terminates);
> +
> +    return qemu_get_ram_fd(mr->ram_addr & TARGET_PAGE_MASK);
> +}
> +
>  void *memory_region_get_ram_ptr(MemoryRegion *mr)
>  {
>      if (mr->alias) {
> -- 
> 1.9.3
> 
> 


-- 
Regards,
  Igor