Re: [Qemu-devel] [PATCH v2] Add option to mlock qemu and guest memory

[Paolo Bonzini <pbonzini@redhat.com>]

Il 14/02/2013 21:21, Satoru Moriya ha scritto:
> We have some plans to migrate legacy enterprise systems which require
> low latency (10 msec order) to kvm virtualized environment. In our
> usecase, the system runs with other untrusted guests and so locking
> memory which is used by the system is needed to avoid latency
> impacts from other guests' memory activity.
> 
> ChangeLog:
> v2
>  - Change the option name from -mlock to -realtime mlock=on|off
>  - Rebase qemu version 1.3.91
>  - Update patch description
> 
> ---
> 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>

As a follow up it would be nice to move -mem-prealloc/-mem-path under
-realtime as well.

Paolo

> ---
>  include/sysemu/os-posix.h |  1 +
>  include/sysemu/os-win32.h |  1 +
>  os-posix.c                |  8 ++++++++
>  qemu-options.hx           | 13 +++++++++++++
>  vl.c                      | 31 +++++++++++++++++++++++++++++++
>  5 files changed, 54 insertions(+)
> 
> diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h
> index 7f198e4..2f2ead6 100644
> --- a/include/sysemu/os-posix.h
> +++ b/include/sysemu/os-posix.h
> @@ -31,6 +31,7 @@ void os_set_proc_name(const char *s);
>  void os_setup_signal_handling(void);
>  void os_daemonize(void);
>  void os_setup_post(void);
> +void os_mlock(void);
>  
>  typedef struct timeval qemu_timeval;
>  #define qemu_gettimeofday(tp) gettimeofday(tp, NULL)
> diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
> index bf9edeb..a74ca13 100644
> --- a/include/sysemu/os-win32.h
> +++ b/include/sysemu/os-win32.h
> @@ -80,6 +80,7 @@ static inline void os_daemonize(void) {}
>  static inline void os_setup_post(void) {}
>  void os_set_line_buffering(void);
>  static inline void os_set_proc_name(const char *dummy) {}
> +static inline void os_mlock(void) {}
>  
>  #if !defined(EPROTONOSUPPORT)
>  # define EPROTONOSUPPORT EINVAL
> diff --git a/os-posix.c b/os-posix.c
> index 5c64518..1304b0e 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -363,3 +363,11 @@ bool is_daemonized(void)
>  {
>      return daemonize;
>  }
> +
> +void os_mlock(void)
> +{
> +    if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
> +        perror("mlockall");
> +        exit(1);
> +    }
> +}
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9d7131a..843fcb4 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -2464,6 +2464,19 @@ STEXI
>  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
> diff --git a/vl.c b/vl.c
> index 1355f69..c16c8ad 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -491,6 +491,18 @@ static QemuOptsList qemu_object_opts = {
>      },
>  };
>  
> +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;
> @@ -1384,6 +1396,17 @@ static void smp_parse(const char *optarg)
>          max_cpus = smp_cpus;
>  }
>  
> +static void configure_realtime(QemuOpts *opts)
> +{
> +    bool is_mlock;
> +
> +    is_mlock = qemu_opt_get_bool(opts, "mlock", true);
> +
> +    if (is_mlock) {
> +        os_mlock();
> +    }
> +}
> +
>  /***********************************************************/
>  /* USB devices */
>  
> @@ -2860,6 +2883,7 @@ int main(int argc, char **argv, char **envp)
>      qemu_add_opts(&qemu_sandbox_opts);
>      qemu_add_opts(&qemu_add_fd_opts);
>      qemu_add_opts(&qemu_object_opts);
> +    qemu_add_opts(&qemu_realtime_opts);
>  
>      runstate_init();
>  
> @@ -3806,6 +3830,13 @@ int main(int argc, char **argv, char **envp)
>                      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);
>              }
>