Re: [Libvirt-cim] [PATCH] Add dynamic VCPU adjustments

23 Jan 2008

Dan Smith wrote:
...
# HG changeset patch
# User Dan Smith <danms@us.ibm.com>
# Date 1201029734 28800
# Node ID 84f80a8040eb29109d0fce50b582582527c2e50e
# Parent  47438edf32be70e65bdb814ab609a70304fad2f4
Add dynamic VCPU adjustments
Signed-off-by: Dan Smith <danms@us.ibm.com>
diff -r 47438edf32be -r 84f80a8040eb libxkutil/device_parsing.c

--- a/libxkutil/device_parsing.c	Tue Jan 22 10:55:59 2008 -0800
+++ b/libxkutil/device_parsing.c	Tue Jan 22 11:22:14 2008 -0800
@@ -897,11 +897,38 @@ static int change_memory(virDomainPtr do
         return 1;
 }
+static int change_vcpus(virDomainPtr dom, int delta)
+{
+        int count = 32;
+        int max;
+        virVcpuInfoPtr foo;
+
+        /* This is retarded, but I don't think there's an API to
+         *   expose the total VCPU number otherwise
+         */
I saw that virDomainInfo contains a field nrVirtCpu. Maybe this is an 
alternative.
...
+        for (max = count; max == count; max += 32) {
+                foo = calloc(max, sizeof(*foo));
+                count = virDomainGetVcpus(dom, foo, max, NULL, 0);
Wouldn't the case "virDomainGetVcpus = 32" cause an endless loop ? On 
the other hand ... I can not quite follow the reason of this for loop, 
which exits right after the first run in case of "count < 32" ?
...
+                free(foo);
+        }
+
+        CU_DEBUG("Changing VCPUs of %s from %i to %i",
+                 virDomainGetName(dom),
+                 count,
+                 count + delta);
+
+        virDomainSetVcpus(dom, count + delta);
This function returns -1 in case of failure. Shouldn't this error case 
be reported to the caller ? With the current setup the caller expects 
that everything worked.
...
+
+        return 1;
+}
+
 int attach_device(virDomainPtr dom, struct virt_device *dev)
 {
         if ((dev->type == VIRT_DEV_NET) ||
             (dev->type == VIRT_DEV_DISK))
                 return _change_device(dom, dev, true);
+        else if (dev->type == VIRT_DEV_VCPU)
+                return change_vcpus(dom, 1);
CU_DEBUG("Unhandled device type %i", dev->type);
@@ -913,6 +940,8 @@ int detach_device(virDomainPtr dom, stru
         if ((dev->type == VIRT_DEV_NET) ||
             (dev->type == VIRT_DEV_DISK))
                 return _change_device(dom, dev, false);
+        else if (dev->type == VIRT_DEV_VCPU)
+                return change_vcpus(dom, -1);
CU_DEBUG("Unhandled device type %i", dev->type);
-- 
Regards

Heidi Eckhart
Software Engineer
IBM Linux Technology Center - Open Hypervisor

    