[mythtv] [mythtv-commits] Ticket #6330: [RFC] New ThreadedFileWriter (lockless)

[Mark Buechler]

Hi

On Mon, May 11, 2009 at 8:32 AM, MythTV <mythtv at cvs.mythtv.org> wrote:

> #6330: [RFC] New ThreadedFileWriter (lockless)
>
> --------------------------------------------------------------+-------------
>  Reporter:  Matthias "mortalmatt" Dahl <devel at mortal-soul.de  |
>  Owner:  ijr
>     Type:  enhancement                                       |
> Status:  new
>  Priority:  minor                                             |
>  Milestone:  0.22
> Component:  MythTV - General                                  |
>  Version:  head
>  Severity:  medium                                            |
> Resolution:
>  Mlocked:  0                                                 |
>
> --------------------------------------------------------------+-------------
>
> Comment(by Matthias "mortalmatt" Dahl <devel at mortal-soul.de>):
>
>  Paul, the old code base is better tested on a wider range of platforms. I
>  have only been able to test this very thoroughly on a x86_64 based machine
>  which ironically uncovered a corruption bug with the old TFW.
>
>  The lockless TFW relies on the atomic operations support of Qt which is
>  not supported natively on all platforms, meaning that they are emulated
>  with e.g. mutexes. Even though I doubt PA-RISC, SH or Blackfin matter for
>  MythTV, so that shouldn't be a problem.
>
>  On PowerPC, S390, MIPS and SH-4a, the atomic operations are supported
>  natively but are not guaranteed to be wait free. I haven't been able to
>  test on those systems, so I can't say how much that affects performance.
>  Based on some research I did and some talking on the Qt irc channel, that
>  won't be a problem too performance wise but I still would like to see some
>  profiling data (old TFW vs. lockless TFW) for those systems, if they
>  matter for MythTV... I guess PowerPC still does?
>
>  That's all that jumps to my mind actually. Like I initially said, I trust
>  it enough to use it myself. :-)
>
> Matthias, can you explain the x86_64 corruption you saw?

Thanks, Mark.
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