[CRIU] Memory dump time with incremental checkpoint

[Ranjan Sarpangala Venkatesh]

Hi Radostin

Thank you for the reply. The transfers, in this case, are done locally to
an image file. I have looked at the code which dumps memory locally.
TIME_MEMWRITE is mostly spliced () of pages and writing pagecache map.
Would like to know why Dump 2 takes much longer while writing less number
of pages. Is it due to the behavior of splice(), trying to sync to the
filesystem or is it due to SPLICE_F_MOVE flag to splice()? Thanks

Regards
Ranjan

On Thu, May 24, 2018 at 2:59 AM Radostin Stoyanov <rstoyanov1 at gmail.com>
wrote:

> Hi Ranjan,
>
> memwrite_time: Time criu spend transferring memory pages into image files
> (locally or on page-server)
> pages_written: The total number of pages criu put into image files
>
> You can find more information about the times measured by criu in
> https://criu.org/Statistics
> Also you can see these times with the --display-stats option.
>
> Regards,
> Radostin
>
> On 24/05/18 03:58, Ranjan Sarpangala Venkatesh wrote:
>
> Hi,
>
> Following are the statistics collected while creating incremental dumps of
> an application using
>
> criu dump --tree $PID --images-dir ./checkpoints/$i/ --leave-running -vvv
> -o dump.log
>
> Dump 1, "pages_written": 2832, "memwrite_time": 11743,
> Dump 2,  "pages_written": 2034, "memwrite_time": 45700,
>
> Dump 2 takes much longer while writing less number of pages. Is this due
> to behavior of splice(). Custom kernel version based on 4.10.0. Any
> insights would be helpful. Thanks
>
> $crit show 1/stats-dump
> {
>     "magic": "STATS",
>     "entries": [
>         {
>             "dump": {
>                 "freezing_time": 273,
>                 "frozen_time": 24271,
>                 "memdump_time": 14884,
>                 "memwrite_time": 11743,
>                 "pages_scanned": 9566,
>                 "pages_skipped_parent": 0,
>                 "pages_written": 2832,
>                 "irmap_resolve": 0
>             }
>         }
>     ]
> }
>
> $crit show 2/stats-dump
> {
>     "magic": "STATS",
>     "entries": [
>         {
>             "dump": {
>                 "freezing_time": 122,
>                 "frozen_time": 55545,
>                 "memdump_time": 49705,
>                 "memwrite_time": 45700,
>                 "pages_scanned": 5873,
>                 "pages_skipped_parent": 0,
>                 "pages_written": 2034,
>                 "irmap_resolve": 0
>             }
>         }
>     ]
> }
>
> Regards
> Ranjan
>
>
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