On Thu, 28 Jun 2012 11:25:10 +0200
Jan Kiszka <jan.kis...@siemens.com> wrote:
> On 2012-06-27 18:49, Luiz Capitulino wrote:
> > Allows to disable memory merge support (KSM on Linux), which is enabled
> > by default otherwise.
> >
> > Signed-off-by: Luiz Capitulino <lcapitul...@redhat.com>
> > ---
> > exec.c | 19 ++++++++++++++++---
> > qemu-config.c | 4 ++++
> > qemu-options.hx | 5 ++++-
> > 3 files changed, 24 insertions(+), 4 deletions(-)
> >
> > diff --git a/exec.c b/exec.c
> > index 8244d54..24dd154 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -2499,6 +2499,19 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char
> > *name, DeviceState *dev)
> > }
> > }
> >
> > +static int madvise_mergeable(void *addr, size_t len)
> > +{
> > + QemuOpts *opts;
> > +
> > + opts = qemu_opts_find(qemu_find_opts("machine"), 0);
> > + if (opts && !qemu_opt_get_bool(opts, "mem_merge", true)) {
> > + /* disabled by the user */
> > + return 0;
> > + }
> > +
> > + return qemu_madvise(addr, len, QEMU_MADV_MERGEABLE);
> > +}
> > +
> > ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
> > MemoryRegion *mr)
> > {
> > @@ -2518,7 +2531,7 @@ 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 +2558,7 @@ 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 +2685,7 @@ 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/qemu-config.c b/qemu-config.c
> > index 5c3296b..e47612e 100644
> > --- a/qemu-config.c
> > +++ b/qemu-config.c
> > @@ -595,6 +595,10 @@ static QemuOptsList qemu_machine_opts = {
> > .name = "dt_compatible",
> > .type = QEMU_OPT_STRING,
> > .help = "Overrides the \"compatible\" property of the dt root
> > node",
> > + }, {
> > + .name = "mem_merge",
> > + .type = QEMU_OPT_BOOL,
> > + .help = "enable/disable memory merge support",
> > },
> > { /* End of list */ }
> > },
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 8b66264..e0e7686 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -33,7 +33,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
> > " property accel=accel1[:accel2[:...]] selects
> > accelerator\n"
> > " supported accelerators are kvm, xen, tcg (default:
> > tcg)\n"
> > " kernel_irqchip=on|off controls accelerated irqchip
> > support\n"
> > - " kvm_shadow_mem=size of KVM shadow MMU\n",
> > + " kvm_shadow_mem=size of KVM shadow MMU\n"
> > + " mem_merge=on|off controls memory merge support
> > (default: on)\n",
> > QEMU_ARCH_ALL)
> > STEXI
> > @item -machine [type=]@var{name}[,prop=@var{value}[,...]]
> > @@ -50,6 +51,8 @@ to initialize.
> > Enables in-kernel irqchip support for the chosen accelerator when
> > available.
> > @item kvm_shadow_mem=size
> > Defines the size of the KVM shadow MMU.
> > +@item mem_merge=on|off
> > +Enables or disables memory merge support (enabled by default).
>
> Describe it as memory deduplication? Just a suggestion. Interface looks
> good to me now.
I can extend the manpage description to read:
Enables or disables memory merge support. This feature, when supported by
the host, de-duplicates identical memory pages among VMs instances.
(enabled by default).
