Commit 8490fc78 authored by Luiz Capitulino's avatar Luiz Capitulino Committed by Anthony Liguori
Browse files

add -machine mem-merge=on|off option 



It allows to disable memory merge support (KSM on Linux), which is
enabled by default otherwise.

Signed-off-by: default avatarLuiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 89c33337

exec.c

+16 −3
Original line number Diff line number Diff line
@@ -2525,6 +2525,19 @@ 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)

{
@@ -2544,7 +2557,7 @@ 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");
@@ -2559,7 +2572,7 @@ 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;
@@ -2689,7 +2702,7 @@ 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);

                qemu_ram_setup_dump(vaddr, length);

            }

            return;

qemu-config.c

+4 −0
Original line number Diff line number Diff line
@@ -615,6 +615,10 @@ static QemuOptsList qemu_machine_opts = { 
            .name = "dump-guest-core",

            .type = QEMU_OPT_BOOL,

            .help = "Include guest memory in  a core dump",

        }, {

            .name = "mem-merge",

            .type = QEMU_OPT_BOOL,

            .help = "enable/disable memory merge support",

        },

        { /* End of list */ }

    },

qemu-options.hx

+6 −1
Original line number Diff line number Diff line
@@ -38,7 +38,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \ 
    "                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"

    "                dump-guest-core=on|off include guest memory in a core dump (default=on)\n",

    "                dump-guest-core=on|off include guest memory in a core dump (default=on)\n"

    "                mem-merge=on|off controls memory merge support (default: on)\n",

    QEMU_ARCH_ALL)

STEXI

@item -machine [type=]@var{name}[,prop=@var{value}[,...]]
@@ -57,6 +58,10 @@ Enables in-kernel irqchip support for the chosen accelerator when available. 
Defines the size of the KVM shadow MMU.

@item dump-guest-core=on|off

Include guest memory in a core dump. The default is on.

@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