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[Qemu-devel] [PATCH v5] add -machine mem-merge=on|off option
From: |
Luiz Capitulino |
Subject: |
[Qemu-devel] [PATCH v5] add -machine mem-merge=on|off option |
Date: |
Wed, 5 Sep 2012 16:50:16 -0300 |
It allows to disable memory merge support (KSM on Linux), which is
enabled by default otherwise.
Signed-off-by: Luiz Capitulino <address@hidden>
---
v5
- rebase on top of current master
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 5834766..c0fbd5b 100644
--- a/exec.c
+++ b/exec.c
@@ -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;
diff --git a/qemu-config.c b/qemu-config.c
index c05ffbc..75763d3 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -612,6 +612,10 @@ 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 */ }
},
diff --git a/qemu-options.hx b/qemu-options.hx
index 3c411c4..90328d0 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -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 address@hidden,address@hidden,...]]
@@ -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.
address@hidden 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
--
1.7.11.2.249.g31c7954.dirty
- [Qemu-devel] [PATCH v5] add -machine mem-merge=on|off option,
Luiz Capitulino <=