[Qemu-devel] [PULL 03/21] qdev: Do not use slow [*] expansion for GPIO creation

["Andreas Färber" <afaerber@suse.de>]

From: Pavel Fedin <p.fedin@samsung.com>

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 <p.fedin@samsung.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
---
 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 a24493a..4ab04aa 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)
-- 
2.1.4