Re: [PATCH 0/3] Report guest steal time in host

Naveen N. Rao
2015-05-06T11:55:17Z

Arrgh! Sorry about the headers. Please ignore this set. Will repost in a
separate thread.

- Naveen

On 2015/05/06 04:28PM, Naveen N Rao wrote:
> Steal time accounts the time duration during which a guest vcpu was ready to
> run, but was not scheduled to run by the hypervisor. This is particularly
> relevant in cloud environment where customers would want to use this as an
> indicator that their guests are being throttled. However, as it stands today,
> guest steal time information is not visible from the hypervisor.
>
> For cloud service providers, this is problematic since they would want to
> overcommit cpu resources to achieve optimum resource utilization while at the
> same time ensuring guests are not throttled. It is useful for service providers
> to have access to the guest steal time data so that they can base their
> overcommit/guest packing decisions on this. Higher guest steal time can be used
> as a trigger to change how the guests are scheduled, or even migrate guests out
> of a system.
>
> This patchset attempts to make the guest steal times available in the host.
> This is achieved by introducing a new field in per-task statistics
> (/proc/<pid>/stat and /proc/<pid>/task/<pid>/stat) to accumulate per-vcpu steal
> time. Programs (such as pidstat) can then be enhanced to report this
> information on a per-thread basis.
>
> This should also work for nested virtualization: steal time information for the
> guest is readable via /proc/stat, while steal time information for guests
> hosted on this hypervisor is readable via /proc/<pid>/task/*/stat.
>
> Also, mpstat always shows steal time information for current (self) guest on a
> per-cpu basis. And pidstat can be enhanced to report the same for the hosted
> guests on a per-vcpu basis.
>
> As an example:
>
> Guest (self) steal time information using mpstat:
> ------------------------------------------------
>
> mpstat is run from within the guest.
>
> [root@rhel7-img ~]# mpstat -P ALL 1
> Linux 3.19.0nnr (rhel7-img) 04/15/2015 _ppc64_ (4 CPU)
>
> 03:13:23 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle
> 03:13:24 PM all 12.25 0.00 1.25 0.00 1.00 2.25 13.75 0.00 0.00 69.50
> 03:13:24 PM 0 46.53 0.00 0.00 0.00 0.00 4.95 45.54 0.00 0.00 2.97
> 03:13:24 PM 1 0.00 0.00 0.00 0.00 0.00 4.04 3.03 0.00 0.00 92.93
> 03:13:24 PM 2 0.00 0.00 0.00 0.00 3.96 0.99 2.97 0.00 0.00 92.08
> 03:13:24 PM 3 3.00 0.00 4.00 0.00 0.00 0.00 4.00 0.00 0.00 89.00
>
> 03:13:24 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle
> 03:13:25 PM all 12.59 0.00 0.00 0.00 0.00 0.25 12.35 0.00 0.00 74.81
> 03:13:25 PM 0 50.00 0.00 0.00 0.00 0.00 0.98 49.02 0.00 0.00 0.00
> 03:13:25 PM 1 0.98 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 99.02
> 03:13:25 PM 2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
> 03:13:25 PM 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
>
> 03:13:25 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle
> 03:13:26 PM all 12.99 0.00 0.00 0.00 0.25 0.00 12.75 0.00 0.00 74.02
> 03:13:26 PM 0 51.96 0.00 0.00 0.00 0.00 0.00 48.04 0.00 0.00 0.00
> 03:13:26 PM 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
> 03:13:26 PM 2 0.00 0.00 0.00 0.00 0.98 0.00 2.94 0.00 0.00 96.08
> 03:13:26 PM 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
>
> 03:13:26 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle
> 03:13:27 PM all 12.53 0.00 1.00 0.25 0.00 0.25 12.03 0.00 0.00 73.93
> 03:13:27 PM 0 51.02 0.00 0.00 0.00 0.00 0.00 48.98 0.00 0.00 0.00
> 03:13:27 PM 1 0.00 0.00 4.04 0.00 0.00 0.00 0.00 0.00 0.00 95.96
> 03:13:27 PM 2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
> 03:13:27 PM 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
>
> Average: CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle
> Average: all 12.91 0.00 0.54 0.01 0.04 0.12 12.39 0.00 0.00 74.00
> Average: 0 51.36 0.00 0.03 0.00 0.03 0.26 48.27 0.00 0.00 0.05
> Average: 1 0.02 0.00 1.54 0.02 0.02 0.15 0.36 0.00 0.00 97.89
> Average: 2 0.00 0.00 0.52 0.00 0.09 0.02 0.36 0.00 0.00 99.02
> Average: 3 0.05 0.00 0.07 0.00 0.02 0.09 0.34 0.00 0.00 99.43
>
> Steal time information for hosted guests in host using (locally modified) pidstat:
> ---------------------------------------------------------------------------------
>
> pidstat is being run in the host.
>
> [naveen@xxxxxxxxxx sysstat]$ ./pidstat -C qemu -tIu 1
> Linux 3.19.0nnr (xxxxxxxxxx.in.ibm.com) 04/15/2015 _ppc64_ (64 CPU)
>
> 04:43:20 AM UID TGID TID %usr %system %guest %CPU %steal CPU Command
> 04:43:22 AM 1008 3001 - 0.00 0.00 54.21 3.39 45.79 12 qemu-system-ppc
> 04:43:22 AM 1008 - 3005 0.00 0.00 54.21 3.39 0.00 12 |__qemu-system-ppc
>
> 04:43:22 AM UID TGID TID %usr %system %guest %CPU %steal CPU Command
> 04:43:23 AM 1008 3001 - 0.00 0.00 52.00 3.25 46.00 12 qemu-system-ppc
> 04:43:23 AM 1008 - 3003 0.00 0.00 2.00 0.12 46.00 12 |__qemu-system-ppc
> 04:43:23 AM 1008 - 3005 0.00 0.00 45.00 2.81 0.00 12 |__qemu-system-ppc
> 04:43:23 AM 1008 - 3006 0.00 0.00 6.00 0.38 0.00 12 |__qemu-system-ppc
>
> 04:43:23 AM UID TGID TID %usr %system %guest %CPU %steal CPU Command
> 04:43:24 AM 1008 3001 - 0.00 2.00 50.00 3.25 67.00 12 qemu-system-ppc
> 04:43:24 AM 1008 - 3001 0.00 1.00 0.00 0.06 0.00 12 |__qemu-system-ppc
> 04:43:24 AM 1008 - 3003 0.00 0.00 8.00 0.50 49.00 12 |__qemu-system-ppc
> 04:43:24 AM 1008 - 3004 0.00 0.00 2.00 0.12 5.00 12 |__qemu-system-ppc
> 04:43:24 AM 1008 - 3005 0.00 0.00 38.00 2.38 3.00 12 |__qemu-system-ppc
> 04:43:24 AM 1008 - 3006 0.00 1.00 0.00 0.06 8.00 12 |__qemu-system-ppc
>
> 04:43:24 AM UID TGID TID %usr %system %guest %CPU %steal CPU Command
> 04:43:25 AM 1008 3001 - 0.00 0.00 51.00 3.19 47.00 12 qemu-system-ppc
> 04:43:25 AM 1008 - 3003 0.00 0.00 27.00 1.69 47.00 12 |__qemu-system-ppc
> 04:43:25 AM 1008 - 3004 0.00 1.00 0.00 0.06 0.00 12 |__qemu-system-ppc
> 04:43:25 AM 1008 - 3005 0.00 1.00 23.00 1.50 0.00 12 |__qemu-system-ppc
> 04:43:25 AM 1008 - 3006 0.00 0.00 2.00 0.12 0.00 12 |__qemu-system-ppc
>
> 04:43:25 AM UID TGID TID %usr %system %guest %CPU %steal CPU Command
> 04:43:26 AM 1008 3001 - 0.00 0.00 51.00 3.18 53.00 12 qemu-system-ppc
> 04:43:26 AM 1008 - 3003 0.00 0.00 9.00 0.56 50.00 12 |__qemu-system-ppc
> 04:43:26 AM 1008 - 3005 0.00 0.00 16.00 1.00 3.00 12 |__qemu-system-ppc
> 04:43:26 AM 1008 - 3006 0.00 0.00 26.00 1.62 0.00 12 |__qemu-system-ppc
>
> Average: UID TGID TID %usr %system %guest %CPU %steal CPU Command
> Average: 1008 3001 - 0.00 0.18 51.54 3.23 50.12 - qemu-system-ppc
> Average: 1008 - 3001 0.02 0.02 0.00 0.00 0.00 - |__qemu-system-ppc
> Average: 1008 - 3003 0.00 0.03 15.89 0.99 48.24 - |__qemu-system-ppc
> Average: 1008 - 3004 0.00 0.05 11.70 0.73 0.56 - |__qemu-system-ppc
> Average: 1008 - 3005 0.00 0.06 20.03 1.26 0.58 - |__qemu-system-ppc
> Average: 1008 - 3006 0.00 0.03 3.93 0.25 0.72 - |__qemu-system-ppc
>
>
> Thanks!
> - Naveen
>
> ------
> Changes since RFC: Updated description to clarify few aspects that I got
> questions about. No code changes.
>
>
> Naveen N. Rao (3):
> procfs: add guest steal time in /proc/<pid>/stat
> kvm/x86: report guest steal time in host
> kvm/powerpc: report guest steal time in host
>
> arch/powerpc/include/asm/kvm_host.h | 1 +
> arch/powerpc/kernel/asm-offsets.c | 1 +
> arch/powerpc/kvm/book3s_hv.c | 2 ++
> arch/powerpc/kvm/book3s_hv_rmhandlers.S | 3 +++
> arch/x86/kvm/x86.c | 1 +
> fs/proc/array.c | 6 ++++++
> include/linux/sched.h | 7 +++++++
> kernel/fork.c | 2 +-
> 8 files changed, 22 insertions(+), 1 deletion(-)
>
> --
> 2.3.5
>