maria-discuss team mailing list archive

[Paul McCullagh <paul.mccullagh@xxxxxxxxxxxxx>]

On Jun 6, 2011, at 11:23 AM, Michael Widenius wrote:

> Hi!
>
> > > > > > "Paul" == Paul McCullagh <paul.mccullagh@xxxxxxxxxxxxx> writes:
>
> Paul> The intension of this code was to set the priority of the  
> current
> Paul> running thread only, not the entire program.
>
> Paul> If the code is not working in this manner, then there is no  
> better
> Paul> solution that to disable it.
>
> Paul> However it would be nice in the cases where  
> pthread_setschedparam()
> Paul> does work, that it is called.
>
> Agree, but I don't know how to test for this case :(
> At least on linux, using setpriority() will not work with any modern  
> Linux.
>
> Paul> In the current code, pthread_setschedparam() is called when
> Paul> pth_min_priority != pth_max_priority.
>
> Current code ?
>
> Do you mean that this has been changed recently ?

No, this has not been changed in years.

> (It was not a long time ago when we merged with the latest pbxt, so I
> assumed we have the latest code already).
>
> The pbxt code in the MariaDB tree is bascily:
> (from xt_p_set_low_priority()):
>
> if (pth_min_priority == pth_max_priority)
> setpriority()
> else
> pth_set_priority()
>
> It's the call to setpriority() that should be avoided in all cases.
>
> Don't see how to fix this for linux except by adding an ifdef around
> the call to setpriority().
>
>
> Do you know of any system, except old obsolete linux systems, where  
> one should
> use setpriority() to set the priority for a thread?

I have done no research on this, so I think we should simply change  
the code to:

 if (pth_min_priority != pth_max_priority)
    pth_set_priority()

This would mean the thread priority is not changed, but that better  
than mistakingly changing the program priority.



--
Paul McCullagh
PrimeBase Technologies
www.primebase.org
www.blobstreaming.org
pbxt.blogspot.com