[Qemu-devel] [PATCH RESEND] apic: Don't iterate past last used apic

[Qemu-devel] [PATCH RESEND] apic: Don't iterate past last used apic

[Alex Williamson]

local_apics are allocated sequentially and never removed, so
we can stop any iterations that go to MAX_APICS as soon as we
hit the first NULL.  Looking at a small guest running a virtio-net
workload with oprofile, this drops apic_get_delivery_bitmask()
from #3 in the profile to down in the noise.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 hw/apic.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/hw/apic.c b/hw/apic.c
index 63d62c7..5f4a87c 100644
--- a/hw/apic.c
+++ b/hw/apic.c
@@ -437,6 +437,8 @@ static int apic_find_dest(uint8_t dest)
         apic = local_apics[i];
 	if (apic && apic->id == dest)
             return i;
+        if (!apic)
+            break;
     }
 
     return -1;
@@ -472,6 +474,8 @@ static void apic_get_delivery_bitmask(uint32_t *deliver_bitmask,
                         set_bit(deliver_bitmask, i);
                     }
                 }
+            } else {
+                break;
             }
         }
     }

Re: [Qemu-devel] [PATCH RESEND] apic: Don't iterate past last used apic

[Anthony Liguori]

On 11/05/2010 05:01 PM, Alex Williamson wrote:
> local_apics are allocated sequentially and never removed, so
> we can stop any iterations that go to MAX_APICS as soon as we
> hit the first NULL.  Looking at a small guest running a virtio-net
> workload with oprofile, this drops apic_get_delivery_bitmask()
> from #3 in the profile to down in the noise.
>
> Signed-off-by: Alex Williamson<alex.williamson@redhat.com>
>    

Applied.  Thanks.

Regards,

Anthony LIguori

> ---
>
>   hw/apic.c |    4 ++++
>   1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/hw/apic.c b/hw/apic.c
> index 63d62c7..5f4a87c 100644
> --- a/hw/apic.c
> +++ b/hw/apic.c
> @@ -437,6 +437,8 @@ static int apic_find_dest(uint8_t dest)
>           apic = local_apics[i];
>   	if (apic&&  apic->id == dest)
>               return i;
> +        if (!apic)
> +            break;
>       }
>
>       return -1;
> @@ -472,6 +474,8 @@ static void apic_get_delivery_bitmask(uint32_t *deliver_bitmask,
>                           set_bit(deliver_bitmask, i);
>                       }
>                   }
> +            } else {
> +                break;
>               }
>           }
>       }
>
>
>
>