[libvirt] [PATCH] util:qemu: fix IOThreadinfo always get failed when get running vm status

[lhuang]

On 06/29/2015 04:38 PM, Peter Krempa wrote:
> On Mon, Jun 29, 2015 at 16:22:54 +0800, Luyao Huang wrote:
>> When we use iothreadinfo to get iothread information, we will get
>> error like this:
>>
>>   # virsh iothreadinfo rhel7.0 --live
>>   error: Unable to get domain IOThreads information
>>   error: Unable to encode message payload
>>
>> This is because virProcessGetAffinity() return a bitmap which map_len
>> is too big to send via rpc:
>>
>>   (gdb) p *map
>>   $7 = {max_bit = 262144, map_len = 4096, map = 0x7f9b6c2c0a20}
>>
>> To fix this issue add a new parameter &maxcpu to virProcessGetAffinity()
>> to let callers specify the maxcpu (also in most machine, no need loop
>> 262144 times to check if cpu is set), if set &maxcpu to zero,
>> virProcessGetAffinity() will use default value (262144 or 1024) to
>> create bitmap. This issue was introduced in commit 825df8c.
>>
>> Signed-off-by: Luyao Huang<lhuang at redhat.com>
>> ---
>>   src/qemu/qemu_driver.c | 4 ++--
>>   src/util/virprocess.c  | 7 ++++---
>>   src/util/virprocess.h  | 2 +-
>>   3 files changed, 7 insertions(+), 6 deletions(-)
>>
> I think a better fix will be to make virBitmapToData smarter when
> formatting a bitmap by finding the last set bit rather than formatting
> the full bitmap.
>
> This will avoid re-introducing the maxcpu argument.
>
> The diff for such change is following:
>
> diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c
> index 9abc807..7234f7e 100644
> --- a/src/util/virbitmap.c
> +++ b/src/util/virbitmap.c
> @@ -498,9 +498,12 @@ virBitmapPtr virBitmapNewData(void *data, int len)
>    */
>   int virBitmapToData(virBitmapPtr bitmap, unsigned char **data, int *dataLen)
>   {
> -    int len;
> +    ssize_t len;
>
> -    len = (bitmap->max_bit + CHAR_BIT - 1) / CHAR_BIT;
> +    if ((len = virBitmapLastSetBit(bitmap)) < 0)
> +        len = 1;
> +    else
> +        len = (len + CHAR_BIT - 1) / CHAR_BIT;
>
>       if (VIR_ALLOC_N(*data, len) < 0)
>           return -1;

Okay, i agree with you, and also we need remove the unused parameter in 
qemuDomainHelperGetVcpus() and qemuDomainGetIOThreadsLive()

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 2b530c8..6aa4c90 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1418,13 +1418,9 @@ static int
  qemuDomainHelperGetVcpus(virDomainObjPtr vm, virVcpuInfoPtr info, int 
maxinfo,
                           unsigned char *cpumaps, int maplen)
  {
-    int hostcpus;
      size_t i, v;
      qemuDomainObjPrivatePtr priv = vm->privateData;

-    if ((hostcpus = nodeGetCPUCount()) < 0)
-        return -1;
-
      if (priv->vcpupids == NULL) {
          virReportError(VIR_ERR_OPERATION_INVALID,
                         "%s", _("cpu affinity is not supported"));
@@ -5573,7 +5569,6 @@ qemuDomainGetIOThreadsLive(virQEMUDriverPtr driver,
      qemuMonitorIOThreadInfoPtr *iothreads = NULL;
      virDomainIOThreadInfoPtr *info_ret = NULL;
      int niothreads = 0;
-    int hostcpus;
      size_t i;
      int ret = -1;

@@ -5606,9 +5601,6 @@ qemuDomainGetIOThreadsLive(virQEMUDriverPtr driver,
          goto endjob;
      }

-    if ((hostcpus = nodeGetCPUCount()) < 0)
-        goto endjob;
-
      if (VIR_ALLOC_N(info_ret, niothreads) < 0)
          goto endjob;



Thanks for your quick review.

> Peter

Luyao