[Qemu-devel] [Bug 1261268] Re: save guest running time is more than 450s with AVX running.

[chao zhou]

after re-check , the first bad commit is:
commit 3e469dbfe413c25d48321c3a19ddfae0727dc6e5
Author: Andrea Arcangeli <address@hidden>
Date:   Thu Jul 25 12:11:15 2013 +0200

    exec: always use MADV_DONTFORK

    MADV_DONTFORK prevents fork to fail with -ENOMEM if the default
    overcommit heuristics decides there's too much anonymous virtual
    memory allocated. If the KVM secondary MMU is synchronized with MMU
    notifiers or not, doesn't make a difference in that regard.

    Secondly it's always more efficient to avoid copying the guest
    physical address space in the fork child (so we avoid to mark all the
    guest memory readonly in the parent and so we skip the establishment
    and teardown of lots of pagetables in the child).

    In the common case we can ignore the error if MADV_DONTFORK is not
    available. Leave a second invocation that errors out in the KVM path
    if MMU notifiers are missing and KVM is enabled, to abort in such
    case.

    Signed-off-by: Andrea Arcangeli <address@hidden>
    Tested-By: Benoit Canet <address@hidden>
    Acked-by: Paolo Bonzini <address@hidden>
    Signed-off-by: Gleb Natapov <address@hidden>

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1261268

Title:
  save guest running time is more than 450s with AVX running.

Status in QEMU:
  New

Bug description:
  Environment:
  ------------
  Host OS (ia32/ia32e/IA64):ia32e
  Guest OS (ia32/ia32e/IA64):ia32e
  Guest OS Type (Linux/Windows):linux
  kvm.git Commit:d6d63b51fe3bfea0cf596993afa480b0b3b02c32
  qemu.git Commit:8f84271da83c0e9f92aa7c1c2d0d3875bf0a5cb8
  Host Kernel Version:3.13.0-rc1
  Hardware:Romley_EP, Ivytown_EP

  
  Bug detailed description:
  --------------------------
  when guest running avx , then do save /restore, save guest running time is 
too lomg

  
  Note:
  1.when save guest (migrate "exec:dd of=test.img")sometimes , the file of 
test.img is 29G, running time of save guest is about 900s
  2. this should be a qemu bug:
  kvm          + qemu       =  result
  d6d63b51  + 8f84271d =  bad
  d6d63b51  + b5d54bd4 =  good


  
  Reproduce steps:
  ----------------
  1.qemu-system-x86_64 -enable-kvm -m 1024 -smp 6 -net 
nic,macaddr=00:12:34:43:14:78 -net tap,script=/etc/kvm/qemu-ifup rhel6u4.qcow
  2. scp  /usr/tet/XVS/tsets/control_panel/tools/bin/avx.tar.gz $guest_IP:/root
  3. tar -zxf avx.tar.gz
  4. cd /avx
  5. sh chk_avx.sh &>/dev/null &
  6. ctrl-alt-2
  7. migrate "exec:dd of=test.img"

  Current result:
  ----------------
  running time of save guest is more than 450s

  Expected result:
  ----------------
  running time of save guest is less than 450s

  Basic root-causing log:
  ----------------------

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1261268/+subscriptions