Re: [Qemu-devel] [RFC 1/3] memory: add -disable-mem-merge command-line option

[Jan Kiszka]

On 2012-06-25 18:55, Luiz Capitulino wrote:
> Allow for disabling memory merge support (KSM on Linux), which is
> enabled by default otherwise.

-machine mem_merge=on|off?

Jan

> 
> Signed-off-by: Luiz Capitulino <address@hidden>
> ---
>  cpu-all.h       |  1 +
>  exec-obsolete.h |  1 +
>  exec.c          | 25 +++++++++++++++++++++----
>  memory.c        |  5 +++++
>  memory.h        |  5 +++++
>  qemu-options.hx |  7 +++++++
>  vl.c            |  3 +++
>  7 files changed, 43 insertions(+), 4 deletions(-)
> 
> diff --git a/cpu-all.h b/cpu-all.h
> index 9dc249a..429c1c3 100644
> --- a/cpu-all.h
> +++ b/cpu-all.h
> @@ -484,6 +484,7 @@ typedef struct RAMBlock {
>  } RAMBlock;
>  
>  typedef struct RAMList {
> +    bool merge_memory;
>      uint8_t *phys_dirty;
>      QLIST_HEAD(, RAMBlock) blocks;
>  } RAMList;
> diff --git a/exec-obsolete.h b/exec-obsolete.h
> index 792c831..71faf81 100644
> --- a/exec-obsolete.h
> +++ b/exec-obsolete.h
> @@ -30,6 +30,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void 
> *host,
>  ram_addr_t qemu_ram_alloc(ram_addr_t size, MemoryRegion *mr);
>  void qemu_ram_free(ram_addr_t addr);
>  void qemu_ram_free_from_ptr(ram_addr_t addr);
> +void qemu_set_mem_merge(bool value);
>  
>  struct MemoryRegion;
>  struct MemoryRegionSection;
> diff --git a/exec.c b/exec.c
> index 8244d54..c003789 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -112,7 +112,10 @@ static uint8_t *code_gen_ptr;
>  int phys_ram_fd;
>  static int in_migration;
>  
> -RAMList ram_list = { .blocks = QLIST_HEAD_INITIALIZER(ram_list.blocks) };
> +RAMList ram_list = {
> +    .merge_memory = true,
> +    .blocks = QLIST_HEAD_INITIALIZER(ram_list.blocks)
> +};
>  
>  static MemoryRegion *system_memory;
>  static MemoryRegion *system_io;
> @@ -2499,6 +2502,20 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char 
> *name, DeviceState *dev)
>      }
>  }
>  
> +void qemu_set_mem_merge(bool value)
> +{
> +    ram_list.merge_memory = value;
> +}
> +
> +static int madvise_mergeable(void *addr, size_t len)
> +{
> +    if (ram_list.merge_memory) {
> +        return qemu_madvise(addr, len, QEMU_MADV_MERGEABLE);
> +    }
> +
> +    return -1;
> +}
> +
>  ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
>                                     MemoryRegion *mr)
>  {
> @@ -2518,7 +2535,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, 
> void *host,
>              new_block->host = file_ram_alloc(new_block, size, mem_path);
>              if (!new_block->host) {
>                  new_block->host = qemu_vmalloc(size);
> -                qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE);
> +                madvise_mergeable(new_block->host, size);
>              }
>  #else
>              fprintf(stderr, "-mem-path option unsupported\n");
> @@ -2545,7 +2562,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, 
> void *host,
>                  new_block->host = qemu_vmalloc(size);
>              }
>  #endif
> -            qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE);
> +            madvise_mergeable(new_block->host, size);
>          }
>      }
>      new_block->length = size;
> @@ -2672,7 +2689,7 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
>                              length, addr);
>                      exit(1);
>                  }
> -                qemu_madvise(vaddr, length, QEMU_MADV_MERGEABLE);
> +                madvise_mergeable(vaddr, length);
>              }
>              return;
>          }
> diff --git a/memory.c b/memory.c
> index aab4a31..71789ab 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1439,6 +1439,11 @@ void memory_global_dirty_log_stop(void)
>      MEMORY_LISTENER_CALL_GLOBAL(log_global_stop, Reverse);
>  }
>  
> +void memory_global_set_merge(bool value)
> +{
> +    qemu_set_mem_merge(value);
> +}
> +
>  static void listener_add_address_space(MemoryListener *listener,
>                                         AddressSpace *as)
>  {
> diff --git a/memory.h b/memory.h
> index 740c48e..ac224d4 100644
> --- a/memory.h
> +++ b/memory.h
> @@ -746,6 +746,11 @@ void memory_global_dirty_log_start(void);
>   */
>  void memory_global_dirty_log_stop(void);
>  
> +/**
> + * memory_global_set_merge: enable/disable memory merging done by the host
> + */
> +void memory_global_set_merge(bool value);
> +
>  void mtree_info(fprintf_function mon_printf, void *f);
>  
>  #endif
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 8b66264..324cc97 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -409,6 +409,13 @@ Preallocate memory when using -mem-path.
>  ETEXI
>  #endif
>  
> +DEF("disable-mem-merge", 0, QEMU_OPTION_disable_mem_merge,
> +    "-disable-mem-merge  disable memory merging.", QEMU_ARCH_ALL)
> +STEXI
> address@hidden -disable-mem-merge
> +Disable memory merging. On Linux systems this disables KSM support.
> +ETEXI
> +
>  DEF("k", HAS_ARG, QEMU_OPTION_k,
>      "-k language     use keyboard layout (for example 'fr' for French)\n",
>      QEMU_ARCH_ALL)
> diff --git a/vl.c b/vl.c
> index 1329c30..f81aadf 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2676,6 +2676,9 @@ int main(int argc, char **argv, char **envp)
>                  mem_prealloc = 1;
>                  break;
>  #endif
> +            case QEMU_OPTION_disable_mem_merge:
> +                memory_global_set_merge(false);
> +                break;
>              case QEMU_OPTION_d:
>                  log_mask = optarg;
>                  break;
>

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