Re: [PATCH] sched - Implement priority and fifo support for SCHED_ISO

["Jack O'Quin" <joq@io.com>]

Con Kolivas <kernel@kolivas.org> writes:

> Sure enough I found the bug in less than 5 mins, and it would
> definitely cause this terrible behaviour.
>
> A silly bracket transposition error on my part :P

The corrected version works noticeably better, but still nowhere near
as well as SCHED_FIFO.  The first run had a cluster of really bad
xruns.  The second and third were much better, but still with numerous
small xruns.

  http://www.joq.us/jack/benchmarks/sched-iso-fix/

With a compile running in the background it was a complete failure.
Some kind of big xrun storm triggered a collapse on every attempt.

  http://www.joq.us/jack/benchmarks/sched-iso-fix+compile/

The summary statistics are mixed.  The delay_max is noticeably better
than before, but still much worse than SCHED_FIFO.  But, the xruns are
really bad news...

  http://www.joq.us/jack/benchmarks/.SUMMARY


# sched-iso-fix
Delay Maximum . . . . . . . . : 33894   usecs
Delay Maximum . . . . . . . . :   745   usecs
Delay Maximum . . . . . . . . :   341   usecs

# sched-iso
Delay Maximum . . . . . . . . : 21410   usecs
Delay Maximum . . . . . . . . : 36830   usecs
Delay Maximum . . . . . . . . :  4062   usecs

# sched-fifo
Delay Maximum . . . . . . . . :   347   usecs
Delay Maximum . . . . . . . . :   277   usecs
Delay Maximum . . . . . . . . :   246   usecs
Delay Maximum . . . . . . . . :   199   usecs
Delay Maximum . . . . . . . . :   261   usecs
Delay Maximum . . . . . . . . :   305   usecs

# sched-iso-fix+compile
Delay Maximum . . . . . . . . : 14549   usecs
Delay Maximum . . . . . . . . : 38961   usecs
Delay Maximum . . . . . . . . : 26904   usecs

# sched-iso+compile
Delay Maximum . . . . . . . . : 98909   usecs
Delay Maximum . . . . . . . . : 39414   usecs
Delay Maximum . . . . . . . . : 40294   usecs
Delay Maximum . . . . . . . . : 217192   usecs
Delay Maximum . . . . . . . . : 156989   usecs

# sched-fifo+compile
Delay Maximum . . . . . . . . :   285   usecs
Delay Maximum . . . . . . . . :   269   usecs
Delay Maximum . . . . . . . . :   277   usecs
Delay Maximum . . . . . . . . :   569   usecs
Delay Maximum . . . . . . . . :   461   usecs
Delay Maximum . . . . . . . . :   405   usecs
Delay Maximum . . . . . . . . :   286   usecs
Delay Maximum . . . . . . . . :   579   usecs

# sched-iso-fix
XRUN Count  . . . . . . . . . :    26
XRUN Count  . . . . . . . . . :    24
XRUN Count  . . . . . . . . . :    17

# sched-iso
XRUN Count  . . . . . . . . . :    15
XRUN Count  . . . . . . . . . :    17
XRUN Count  . . . . . . . . . :     5

# sched-fifo
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0

# sched-iso-fix+compile
XRUN Count  . . . . . . . . . :    22
XRUN Count  . . . . . . . . . :    44
XRUN Count  . . . . . . . . . :    39

# sched-iso+compile
XRUN Count  . . . . . . . . . :    44
XRUN Count  . . . . . . . . . :    46
XRUN Count  . . . . . . . . . :    45
XRUN Count  . . . . . . . . . :    27
XRUN Count  . . . . . . . . . :   101

# sched-fifo+compile
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     4
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0

-- 
  joq