Re: [libvirt] [PATCH] Host cpu offline/online removes the cpus available for vms

2014-02-04 Thread Shivaprasad bhat 
Hi Eric,

Came across a thread where the kernel stands not to change the
cpuset's behavior during the online-offline-online scenario.

https://lkml.org/lkml/2012/5/4/265

Hope fixing this in Libvirt makes more sense now.

Regards,
Shivaprasad G Bhat

On Sat, Feb 1, 2014 at 8:49 AM, Shivaprasad bhat
shivaprasadb...@gmail.com wrote:
 Thanks for the comments Eric.

 The offline, removes the entry from the cgroups and all its subcgroups.
 On Online, I guess kernel does not know till which sub-cgroup it
 should add the entry.
 I think that is how cgroup is designed to behave when it lacks the
 policy knowledge.
 Let me know what you think.

 Regards,
 Shivaprasad G Bhat

 On Fri, Jan 31, 2014 at 9:58 PM, Eric Blake ebl...@redhat.com wrote:
 On 01/31/2014 12:22 AM, Shivaprasad G Bhat wrote:
 Online/Offline operations on the host cpus removes the machine/cpuset.cpus
 which are never added back. The guests with vcpu pinning can fail to boot
 unless the xml is edited.

 If the possibility that the offlined cpus are onlined back, the cpuset.cpus 
 can be updated upon start of the guest thus allowing the guests to boot 
 back without
 erroring out.

 Please wrap commit message lines; typically, wrapping less than 70
 characters since 'git log' indents the lines.


 Signed-off-by: Shivaprasad G Bhat sb...@linux.vnet.ibm.com
 ---
  src/util/vircgroup.c |   27 +--
  1 file changed, 17 insertions(+), 10 deletions(-)

 diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
 index a6d60c5..52575c9 100644
 --- a/src/util/vircgroup.c
 +++ b/src/util/vircgroup.c
 @@ -72,6 +72,7 @@ typedef enum {
 * before creating subcgroups and
 * attaching tasks
 */
 +VIR_CGROUP_CPUS_HIERACHY = 1  1, /* call virCgroupCpuSetInherit */

 s/HIERACHY/HIERARCHY/

 I'm not sure about the technical aspect of this patch, on whether this
 is the best approach to deal with the situation.  I think the kernel has
 caused several issues with how it handles offline cpu vs. cgroups, and
 wonder if the fix belongs in the kernel.

 --
 Eric Blake   eblake redhat com+1-919-301-3266
 Libvirt virtualization library http://libvirt.org


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[libvirt] [PATCH] Host cpu offline/online removes the cpus available for vms

2014-01-31 Thread Shivaprasad G Bhat 
Online/Offline operations on the host cpus removes the machine/cpuset.cpus
which are never added back. The guests with vcpu pinning can fail to boot
unless the xml is edited.

If the possibility that the offlined cpus are onlined back, the cpuset.cpus can 
be updated upon start of the guest thus allowing the guests to boot back without
erroring out.

Signed-off-by: Shivaprasad G Bhat sb...@linux.vnet.ibm.com
---
 src/util/vircgroup.c |   27 +--
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
index a6d60c5..52575c9 100644
--- a/src/util/vircgroup.c
+++ b/src/util/vircgroup.c
@@ -72,6 +72,7 @@ typedef enum {
* before creating subcgroups and
* attaching tasks
*/
+VIR_CGROUP_CPUS_HIERACHY = 1  1, /* call virCgroupCpuSetInherit */
 } virCgroupFlags;
 
 
@@ -891,6 +892,7 @@ virCgroupMakeGroup(virCgroupPtr parent,
 VIR_DEBUG(Make group %s, group-path);
 for (i = 0; i  VIR_CGROUP_CONTROLLER_LAST; i++) {
 char *path = NULL;
+int inheritCpuset = 0;
 
 /* We must never mkdir() in systemd's hierarchy */
 if (i == VIR_CGROUP_CONTROLLER_SYSTEMD) {
@@ -933,15 +935,7 @@ virCgroupMakeGroup(virCgroupPtr parent,
 goto cleanup;
 }
 }
-if (group-controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint != 
NULL 
-(i == VIR_CGROUP_CONTROLLER_CPUSET ||
- STREQ(group-controllers[i].mountPoint,
-   
group-controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint))) {
-if (virCgroupCpuSetInherit(parent, group)  0) {
-VIR_FREE(path);
-goto cleanup;
-}
-}
+inheritCpuset = 1;
 /*
  * Note that virCgroupSetMemoryUseHierarchy should always be
  * called prior to creating subcgroups and attaching tasks.
@@ -958,6 +952,19 @@ virCgroupMakeGroup(virCgroupPtr parent,
 }
 }
 
+if (inheritCpuset || (flags  VIR_CGROUP_CPUS_HIERACHY))
+{
+if (group-controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint != 
NULL 
+(i == VIR_CGROUP_CONTROLLER_CPUSET ||
+ STREQ(group-controllers[i].mountPoint,
+   
group-controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint))) {
+if (virCgroupCpuSetInherit(parent, group)  0) {
+VIR_FREE(path);
+goto cleanup;
+}
+}
+}
+
 VIR_FREE(path);
 }
 
@@ -1275,7 +1282,7 @@ virCgroupNewPartition(const char *path,
 if (virCgroupNew(-1, parentPath, NULL, controllers, parent)  0)
 goto cleanup;
 
-if (virCgroupMakeGroup(parent, *group, create, VIR_CGROUP_NONE)  0) {
+if (virCgroupMakeGroup(parent, *group, create, 
VIR_CGROUP_CPUS_HIERACHY)  0) {
 virCgroupRemove(*group);
 goto cleanup;
 }

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Re: [libvirt] [PATCH] Host cpu offline/online removes the cpus available for vms

2014-01-31 Thread Eric Blake 
On 01/31/2014 12:22 AM, Shivaprasad G Bhat wrote:
 Online/Offline operations on the host cpus removes the machine/cpuset.cpus
 which are never added back. The guests with vcpu pinning can fail to boot
 unless the xml is edited.
 
 If the possibility that the offlined cpus are onlined back, the cpuset.cpus 
 can be updated upon start of the guest thus allowing the guests to boot back 
 without
 erroring out.

Please wrap commit message lines; typically, wrapping less than 70
characters since 'git log' indents the lines.

 
 Signed-off-by: Shivaprasad G Bhat sb...@linux.vnet.ibm.com
 ---
  src/util/vircgroup.c |   27 +--
  1 file changed, 17 insertions(+), 10 deletions(-)
 
 diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
 index a6d60c5..52575c9 100644
 --- a/src/util/vircgroup.c
 +++ b/src/util/vircgroup.c
 @@ -72,6 +72,7 @@ typedef enum {
 * before creating subcgroups and
 * attaching tasks
 */
 +VIR_CGROUP_CPUS_HIERACHY = 1  1, /* call virCgroupCpuSetInherit */

s/HIERACHY/HIERARCHY/

I'm not sure about the technical aspect of this patch, on whether this
is the best approach to deal with the situation.  I think the kernel has
caused several issues with how it handles offline cpu vs. cgroups, and
wonder if the fix belongs in the kernel.

-- 
Eric Blake   eblake redhat com+1-919-301-3266
Libvirt virtualization library http://libvirt.org



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Re: [libvirt] [PATCH] Host cpu offline/online removes the cpus available for vms

2014-01-31 Thread Shivaprasad bhat 
Thanks for the comments Eric.

The offline, removes the entry from the cgroups and all its subcgroups.
On Online, I guess kernel does not know till which sub-cgroup it
should add the entry.
I think that is how cgroup is designed to behave when it lacks the
policy knowledge.
Let me know what you think.

Regards,
Shivaprasad G Bhat

On Fri, Jan 31, 2014 at 9:58 PM, Eric Blake ebl...@redhat.com wrote:
 On 01/31/2014 12:22 AM, Shivaprasad G Bhat wrote:
 Online/Offline operations on the host cpus removes the machine/cpuset.cpus
 which are never added back. The guests with vcpu pinning can fail to boot
 unless the xml is edited.

 If the possibility that the offlined cpus are onlined back, the cpuset.cpus 
 can be updated upon start of the guest thus allowing the guests to boot back 
 without
 erroring out.

 Please wrap commit message lines; typically, wrapping less than 70
 characters since 'git log' indents the lines.


 Signed-off-by: Shivaprasad G Bhat sb...@linux.vnet.ibm.com
 ---
  src/util/vircgroup.c |   27 +--
  1 file changed, 17 insertions(+), 10 deletions(-)

 diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
 index a6d60c5..52575c9 100644
 --- a/src/util/vircgroup.c
 +++ b/src/util/vircgroup.c
 @@ -72,6 +72,7 @@ typedef enum {
 * before creating subcgroups and
 * attaching tasks
 */
 +VIR_CGROUP_CPUS_HIERACHY = 1  1, /* call virCgroupCpuSetInherit */

 s/HIERACHY/HIERARCHY/

 I'm not sure about the technical aspect of this patch, on whether this
 is the best approach to deal with the situation.  I think the kernel has
 caused several issues with how it handles offline cpu vs. cgroups, and
 wonder if the fix belongs in the kernel.

 --
 Eric Blake   eblake redhat com+1-919-301-3266
 Libvirt virtualization library http://libvirt.org


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