Re: [Qemu-devel] [PATCH v4 0/8] Obtain dirty bitmap via VM logging

[Dr. David Alan Gilbert]

* Sanidhya Kashyap (address@hidden) wrote:
> Hi,
> 
> The following patches introduce the support of the dirty bitmap logging and
> dumping to a specified file. This patch addresses the previous issues raised
> by David and Juan. Since, I have not received any comments on the runstates,
> I'll keep them in the patch series.

Hi Sanidhya,
  I've finally got around to reading through your patches.  Some general
thoughts first, and I'll put some more detail on the patches themselves:

1) Do you have some examples of output?
   Can you see hot areas in the kernel or something else?

2) 'frequency' is probably the wrong name for the parameter you have; since
the parameter is actually the delay between epochs, where as frequency
would imply the number of epochs/second.

3) The change to runstates is interesting; up until now 'runstate' is really
mostly about the state of the CPU, but by adding migration/dumping to the
states you're trying to convey more in that single state variable; I'm not
quite sure if this is the right thing to do or not.

Dave

> 
> v3 --> v4
> * Added new qmp interface for information extraction from the bitmap process
> 
> v2 --> v3
> * Reformatted the code and removed some unnecessary parts.
> * Printing block info along with length and offset.
> * Changed the functions that were directly using RUN_STATE_RUNNING as state.
> 
> v1 --> v2:
> * Added two new run states to avoid simultaneous execution of both migration 
> and
>   bitmap dump process.
> * Removed FILE pointer usage.
> * Dumping the data only in machine-readable format.
> * Tried to rectify mistakes of the previous version.
> 
> 
> 
> Sanidhya Kashyap (8):
>   enable sharing of the function between migration and bitmap dump
>   RunState: added two new flags for bitmap dump and migration process
>   BitmapLog: bitmap dump code via QAPI framework with runstates
>   BitmapLog: hmp interface for dirty bitmap dump
>   BitmapLog: cancel mechanism for an already running dump bitmap process
>   BitmapLog: set the frequency of the dump bitmap process
>   BitmapLog: get the information about the parameters
>   BitmapLog: python script for extracting bitmap from a binary file
> 
>  arch_init.c               |  19 ++-
>  hmp-commands.hx           |  45 ++++++
>  hmp.c                     |  33 ++++
>  hmp.h                     |   3 +
>  hw/usb/hcd-ehci.c         |   2 +-
>  hw/usb/redirect.c         |   6 +-
>  include/exec/cpu-all.h    |   4 +-
>  include/exec/ram_addr.h   |   4 +
>  migration.c               |   7 +
>  qapi-schema.json          |  77 +++++++++-
>  qmp-commands.hx           |  99 ++++++++++++
>  savevm.c                  | 384 
> ++++++++++++++++++++++++++++++++++++++++++++++
>  scripts/extract-bitmap.py |  97 ++++++++++++
>  vl.c                      |  29 +++-
>  14 files changed, 794 insertions(+), 15 deletions(-)
>  create mode 100755 scripts/extract-bitmap.py
> 
> -- 
> 1.9.3
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK