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

[Anthony Liguori]

On 06/25/2012 03:26 PM, Jan Kiszka wrote:
> 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?

Ack.

But any reason not to call it ksm=on|off?

Regards,

Anthony Liguori

> 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;