VM memory allocation speed with cs 26056

[Zhigang Wang <zhigang.x.wang@oracle.com>]

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Hi Keir/Jan,

Recently I got a chance to access a big machine (2T mem/160 cpus) and I tested
your patch: http://xenbits.xen.org/hg/xen-unstable.hg/rev/177fdda0be56

Attached is the result.

Test environment old:

      # xm info
      host                   : ovs-3f-9e-04
      release                : 2.6.39-300.17.1.el5uek
      version                : #1 SMP Fri Oct 19 11:30:08 PDT 2012
      machine                : x86_64
      nr_cpus                : 160
      nr_nodes               : 8
      cores_per_socket       : 10
      threads_per_core       : 2
      cpu_mhz                : 2394
      hw_caps                :
bfebfbff:2c100800:00000000:00003f40:02bee3ff:00000000:00000001:00000000
      virt_caps              : hvm hvm_directio
      total_memory           : 2097142
      free_memory            : 2040108
      free_cpus              : 0
      xen_major              : 4
      xen_minor              : 1
      xen_extra              : .3OVM
      xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
      xen_scheduler          : credit
      xen_pagesize           : 4096
      platform_params        : virt_start=0xffff800000000000
      xen_changeset          : unavailable
      xen_commandline        : dom0_mem=31390M no-bootscrub
      cc_compiler            : gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)
      cc_compile_by          : mockbuild
      cc_compile_domain      : us.oracle.com
      cc_compile_date        : Fri Oct 19 21:34:08 PDT 2012
      xend_config_format     : 4

      # uname -a
      Linux ovs-3f-9e-04 2.6.39-300.17.1.el5uek #1 SMP Fri Oct 19 11:30:08 PDT
2012 x86_64 x86_64 x86_64 GNU/Linux

      # cat /boot/grub/grub.conf
      ...
      kernel /xen.gz dom0_mem=31390M no-bootscrub dom0_vcpus_pin dom0_max_vcpus=32

Test environment new: old env + cs 26056

Test script: test-vm-memory-allocation.sh (attached)

My conclusion from the test:

  - HVM create time is greatly reduced.
  - PVM create time is increased dramatically for 4G, 8G, 16G, 32G, 64G, 128G.
  - HVM/PVM destroy time is not affected.
  - If most of our customers are using PVM, I think this patch is bad: because
most VM memory should under 128G.
  - If they are using HVM, then this patch is great.

Questions for discussion:

  - Did you get the same result?
  - It seems this result is not ideal. We may need to improve it.

Please note: Imay not have access to the same machine for awhile.

Thanks,

Zhigang


[-- Attachment #2: result.pdf --]
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[-- Attachment #3: result.csv --]
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memory_size_gb,hvm_old_create,hvm_new_create,pvm_old_create,pvm_new_create,hvm_old_destroy,hvm_new_destroy,pvm_old_destroy,pvm_new_destroy
1,1.159,1.093,3.222,4.034,1.024,1.185,1.020,1.040
2,1.316,0.888,4.408,5.443,1.327,1.961,1.979,1.990
4,1.382,0.962,4.622,8.367,3.633,2.858,2.893,2.901
8,1.440,1.057,4.969,14.272,4.035,5.305,5.337,6.668
16,1.539,1.264,5.607,25.758,12.862,12.828,12.865,12.886
32,1.754,1.665,7.066,48.729,25.302,19.945,19.978,19.987
64,2.188,2.499,9.752,97.022,28.790,39.350,50.048,50.118
128,10.949,4.090,15.234,189.261,57.128,78.240,78.440,78.432
256,418.667,10.275,452.320,375.961,114.851,156.496,198.798,156.391
512,430.449,14.831,494.971,752.235,355.738,353.989,354.502,382.305
1024,867.145,28.570,1004.788,818.385,626.623,747.762,751.686,752.019
1500,1716.501,38.601,1968.900,1599.078,1083.900,1006.805,1000.907,1006.042

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