Re: [Qemu-devel] [PATCH v2] Do not use slow [*] expansion for GPIO creation

[Paolo Bonzini]

On 31/07/2015 14:23, Pavel Fedin wrote:
> Expansion of [*] suffix is very slow because index expansion is done using
> trial and error strategy, starting every time from zero and retrying with
> the next index until insertion succeeds. With large number of already added
> properties this process takes huge amount of time (O(n^2) complexity).
> 
> Some architectures (like ARM) use very large amount of IRQ pins in interrupt
> controller models. This flaw makes machine startup extremely slow
> (~20 seconds for ARM64 with 32 CPUs. This patch decreases this time down to
> ~10 seconds.
> 
> Also in qdev_init_gpio_out_named() memset() is now called only once for the
> whole array instead of per-cell cleaning
> 
> Signed-off-by: Pavel Fedin <address@hidden>
> ---
>  hw/core/qdev.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index b2f404a..1d15736 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -417,17 +417,21 @@ void qdev_init_gpio_in_named(DeviceState *dev, 
> qemu_irq_handler handler,
>  {
>      int i;
>      NamedGPIOList *gpio_list = qdev_get_named_gpio_list(dev, name);
> -    char *propname = g_strdup_printf("%s[*]", name ? name : 
> "unnamed-gpio-in");
>  
>      assert(gpio_list->num_out == 0 || !name);
>      gpio_list->in = qemu_extend_irqs(gpio_list->in, gpio_list->num_in, 
> handler,
>                                       dev, n);
>  
> +    if (!name) {
> +        name = "unnamed-gpio-in";
> +    }
>      for (i = gpio_list->num_in; i < gpio_list->num_in + n; i++) {
> +        gchar *propname = g_strdup_printf("%s[%u]", name, i);
> +
>          object_property_add_child(OBJECT(dev), propname,
>                                    OBJECT(gpio_list->in[i]), &error_abort);
> +        g_free(propname);
>      }
> -    g_free(propname);
>  
>      gpio_list->num_in += n;
>  }
> @@ -442,20 +446,25 @@ void qdev_init_gpio_out_named(DeviceState *dev, 
> qemu_irq *pins,
>  {
>      int i;
>      NamedGPIOList *gpio_list = qdev_get_named_gpio_list(dev, name);
> -    char *propname = g_strdup_printf("%s[*]", name ? name : 
> "unnamed-gpio-out");
>  
>      assert(gpio_list->num_in == 0 || !name);
> -    gpio_list->num_out += n;
>  
> +    if (!name) {
> +        name = "unnamed-gpio-out";
> +    }
> +    memset(pins, 0, sizeof(*pins) * n);
>      for (i = 0; i < n; ++i) {
> -        memset(&pins[i], 0, sizeof(*pins));
> +        gchar *propname = g_strdup_printf("%s[%u]", name,
> +                                          gpio_list->num_out + i);
> +
>          object_property_add_link(OBJECT(dev), propname, TYPE_IRQ,
>                                   (Object **)&pins[i],
>                                   object_property_allow_set_link,
>                                   OBJ_PROP_LINK_UNREF_ON_RELEASE,
>                                   &error_abort);
> +        g_free(propname);
>      }
> -    g_free(propname);
> +    gpio_list->num_out += n;
>  }
>  
>  void qdev_init_gpio_out(DeviceState *dev, qemu_irq *pins, int n)
> 

Thanks, this looks good.  I'm not the maintainer, but I've queued it
anyway locally so that it's not forgotten.

Paolo