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Message-ID: <20150506115517.GA26540@naverao1-tp.in.ibm.com>
Date:	Wed, 6 May 2015 17:25:17 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	kvm@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org
Cc:	paulus@...ba.org, mpe@...erman.id.au, agraf@...e.de,
	mingo@...hat.com, ego@...ux.vnet.ibm.com
Subject: Re: [PATCH 0/3] Report guest steal time in host

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@...l7-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@...xxxxxxx 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
> 

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