commit 888a6bc63c94ef34026399117ebf6a1fa0e7a29a
author Satoru Moriya <satoru.moriya@hds.com> Fri Apr 19 16:42:06 2013 +0200
committer Anthony Liguori <aliguori@us.ibm.com> Mon Apr 22 08:52:23 2013 -0500
tree 9a7eaa7b65500baf6099eb9118c92aa220c3b4f1
parent 2b316774f60291f57ca9ecb6a9f0712c532cae34

Add option to mlock qemu and guest memory

In certain scenario, latency induced by paging is significant and
memory locking is needed. Also, in the scenario with untrusted
guests, latency improvement due to mlock is desired.

This patch introduces a following new option to mlock guest and
qemu memory:

-realtime mlock=on|off

Signed-off-by: Satoru Moriya <satoru.moriya@hds.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1366382526-26146-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

include/sysemu/os-posix.h

diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h
index 7f198e4..25d0b2a 100644
--- a/include/sysemu/os-posix.h
+++ b/include/sysemu/os-posix.h
@@ -31,6 +31,7 @@
 void os_setup_signal_handling(void);
 void os_daemonize(void);
 void os_setup_post(void);
+int os_mlock(void);
 
 typedef struct timeval qemu_timeval;
 #define qemu_gettimeofday(tp) gettimeofday(tp, NULL)

include/sysemu/os-win32.h

diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
index 71f5fa0..bf8523a 100644
--- a/include/sysemu/os-win32.h
+++ b/include/sysemu/os-win32.h
@@ -106,4 +106,9 @@
     return false;
 }
 
+static inline int os_mlock(void)
+{
+    return -ENOSYS;
+}
+
 #endif

os-posix.c

diff --git a/os-posix.c b/os-posix.c
index 5c64518..d39261d 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -363,3 +363,15 @@
 {
     return daemonize;
 }
+
+int os_mlock(void)
+{
+    int ret = 0;
+
+    ret = mlockall(MCL_CURRENT | MCL_FUTURE);
+    if (ret < 0) {
+        perror("mlockall");
+    }
+
+    return ret;
+}

qemu-options.hx

diff --git a/qemu-options.hx b/qemu-options.hx
index 5c115d1..e86cc24 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2583,6 +2583,19 @@
 Do not start CPU at startup (you must type 'c' in the monitor).
 ETEXI
 
+DEF("realtime", HAS_ARG, QEMU_OPTION_realtime,
+    "-realtime [mlock=on|off]\n"
+    "                run qemu with realtime features\n"
+    "                mlock=on|off controls mlock support (default: on)\n",
+    QEMU_ARCH_ALL)
+STEXI
+@item -realtime mlock=on|off
+@findex -realtime
+Run qemu with realtime features.
+mlocking qemu and guest memory can be enabled via @option{mlock=on}
+(enabled by default).
+ETEXI
+
 DEF("gdb", HAS_ARG, QEMU_OPTION_gdb, \
     "-gdb dev        wait for gdb connection on 'dev'\n", QEMU_ARCH_ALL)
 STEXI

vl.c

diff --git a/vl.c b/vl.c
index 2ef00d8..6caa5f4 100644
--- a/vl.c
+++ b/vl.c
@@ -521,6 +521,18 @@
     },
 };
 
+static QemuOptsList qemu_realtime_opts = {
+    .name = "realtime",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_realtime_opts.head),
+    .desc = {
+        {
+            .name = "mlock",
+            .type = QEMU_OPT_BOOL,
+        },
+        { /* end of list */ }
+    },
+};
+
 const char *qemu_get_vm_name(void)
 {
     return qemu_name;
@@ -1420,6 +1432,20 @@
         max_cpus = smp_cpus;
 }
 
+static void configure_realtime(QemuOpts *opts)
+{
+    bool enable_mlock;
+
+    enable_mlock = qemu_opt_get_bool(opts, "mlock", true);
+
+    if (enable_mlock) {
+        if (os_mlock() < 0) {
+            fprintf(stderr, "qemu: locking memory failed\n");
+            exit(1);
+        }
+    }
+}
+
 /***********************************************************/
 /* USB devices */
 
@@ -2862,6 +2888,7 @@
     qemu_add_opts(&qemu_add_fd_opts);
     qemu_add_opts(&qemu_object_opts);
     qemu_add_opts(&qemu_tpmdev_opts);
+    qemu_add_opts(&qemu_realtime_opts);
 
     runstate_init();
 
@@ -3835,6 +3862,13 @@
                     exit(1);
                 }
                 break;
+            case QEMU_OPTION_realtime:
+                opts = qemu_opts_parse(qemu_find_opts("realtime"), optarg, 0);
+                if (!opts) {
+                    exit(1);
+                }
+                configure_realtime(opts);
+                break;
             default:
                 os_parse_cmd_args(popt->index, optarg);
             }