It allows to disable memory merge support (KSM on Linux), which is enabled by default otherwise.
Signed-off-by: Luiz Capitulino <lcapitul...@redhat.com> --- IMPORTANT: this is on top of this series: http://lists.gnu.org/archive/html/qemu-devel/2012-07/msg01798.html o v4 - rename option to mem-merge - rebase on top of latest master - rebase on top of the machine option rename series exec.c | 19 ++++++++++++++++--- qemu-config.c | 4 ++++ qemu-options.hx | 7 ++++++- 3 files changed, 26 insertions(+), 4 deletions(-) diff --git a/exec.c b/exec.c index c9fa17d..59d29ae 100644 --- a/exec.c +++ b/exec.c @@ -2510,6 +2510,19 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char *name, DeviceState *dev) } } +static int memory_try_enable_merging(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) { @@ -2529,7 +2542,7 @@ 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); + memory_try_enable_merging(new_block->host, size); } #else fprintf(stderr, "-mem-path option unsupported\n"); @@ -2544,7 +2557,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, } else { new_block->host = qemu_vmalloc(size); } - qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE); + memory_try_enable_merging(new_block->host, size); } } new_block->length = size; @@ -2670,7 +2683,7 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length) length, addr); exit(1); } - qemu_madvise(vaddr, length, QEMU_MADV_MERGEABLE); + memory_try_enable_merging(vaddr, length); } return; } diff --git a/qemu-config.c b/qemu-config.c index 9dac3be..3355e45 100644 --- a/qemu-config.c +++ b/qemu-config.c @@ -599,6 +599,10 @@ static QemuOptsList qemu_machine_opts = { .alias= "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 90eab87..25ce07e 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 +51,10 @@ 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. This feature, when supported by +the host, de-duplicates identical memory pages among VMs instances +(enabled by default). @end table ETEXI -- 1.7.11.1.116.g8228a23
