Re: [Qemu-devel] [PATCH v3] Add option to mlock qemu and guest memory

[Anthony Liguori <aliguori@us.ibm.com>]

Satoru Moriya <satoru.moriya@hds.com> writes:

> ChangeLog:
> v3
>  - Modify os_mlock() to return error code
>  - Update configure_realtime() to handle return value from os_mlock()
>  - Change the variable name from is_mlock to enable_mlock in configure_realtime()
>  - Rebase qemu version 1.4.50
>
> v2
>  - Change option name from -mlock to -realtime mlock=on|off
>  - Rebase qemu version 1.3.91
>  - Update patch description
>
> 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.
>
> ---

By putting this here, you're going to mess up the commit message.
Everything below '---' gets chopped off.

You want to move the changelog below the --- and the commit message
above it.

Please submit a v4 with a corrected commit message.

Regards,

Anthony Liguori

> 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>
>
> ---
>  include/sysemu/os-posix.h |  1 +
>  include/sysemu/os-win32.h |  5 +++++
>  os-posix.c                | 12 ++++++++++++
>  qemu-options.hx           | 13 +++++++++++++
>  vl.c                      | 34 ++++++++++++++++++++++++++++++++++
>  5 files changed, 65 insertions(+)
>
> 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_set_proc_name(const char *s);
>  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)
> 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 @@ static inline bool is_daemonized(void)
>      return false;
>  }
>  
> +static inline int os_mlock(void)
> +{
> +    return -ENOSYS;
> +}
> +
>  #endif
> 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 @@ bool is_daemonized(void)
>  {
>      return daemonize;
>  }
> +
> +int os_mlock(void)
> +{
> +    int ret = 0;
> +
> +    ret = mlockall(MCL_CURRENT | MCL_FUTURE);
> +    if (ret < 0) {
> +        perror("mlockall");
> +    }
> +
> +    return ret;
> +}
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 06dd565..1ec9541 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -2569,6 +2569,19 @@ 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 aeed7f4..71bbcf1 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -521,6 +521,18 @@ static QemuOptsList qemu_tpmdev_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;
> @@ -1420,6 +1432,20 @@ static void smp_parse(const char *optarg)
>          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 */
>  
> @@ -2909,6 +2935,7 @@ int main(int argc, char **argv, char **envp)
>      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();
>  
> @@ -3878,6 +3905,13 @@ 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);
>              }
> -- 
> 1.7.11.7