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Re: [libvirt] [PATCH] cpustat: fix regression when cpus are offline

On 10/25/12 22:57, Eric Blake wrote:
It turns out that the cpuacct results properly account for offline
cpus, and always returns results for every possible cpu, not just
the online ones.  So there is no need to check the map of online
cpus in the first place, merely only a need to know the maximum
possible cpu.  Meanwhile, virNodeGetCPUBitmap had a subtle change
from returning the maximum id to instead returning the width of
the bitmap (one larger than the maximum id), which made this code
encounter some off-by-one logic leading to bad error messages when
a cpu was offline:

$ virsh cpu-stats dom
error: Failed to virDomainGetCPUStats()

error: An error occurred, but the cause is unknown

* src/qemu/qemu_driver.c (qemuDomainGetPercpuStats): Drop
pointless check for cpumap changes, and use correct number of

Fixes the regression noticed here:

  src/qemu/qemu_driver.c | 26 +++-----------------------
  1 file changed, 3 insertions(+), 23 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 18be7d9..f817319 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -13597,7 +13597,6 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
                           unsigned int ncpus)
      virBitmapPtr map = NULL;
-    virBitmapPtr map2 = NULL;

When you apply this patch "map" is also not needed (never actualy used).

Is there a way to replace
"map = nodeGetCPUBitmap(domain->conn, &max_id);" to get max_id? That's the only thing that code is used to.

      int rv = -1;
      int i, id, max_id;
      char *pos;

Otherwise looks good. (ACK if there isn't any other option to get max_id than to call nodeGetCPUBitmap)


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