8 Mar
2011
8 Mar
'11
7:57 a.m.
On attempt to use device (or even just try 'cat /dev/hpet'), it is said, that
device is busy. But jack has such option :/
I'm using kernel 2.6.33-rt. I can guess, that under rt kernel i should not use HPET
directly, because it is used by system,
and so, may be referred via 'system'. But even if that, such way could bring some
violations comparing to direct HPET usage.
May be indeed, HPET should be used directly only on non-rt systems?..
Btw, how i specified it: i have jack2 and ladish. Clock is specified via ladiconf. Clock
parameter type is integer; yesterday nedko showed me a patch for jack, fixing this
problem, where i saw order of variants in enumeration (hpet variant is '2').
8 Mar
8 Mar
8:59 a.m.
New subject: Can't use HPET by JACK2 under kxstudio (probably, it is ubuntu problem too).
On Tue, 2011-03-08 at 09:57 +0300, Mike Cookson wrote:
On attempt to use device (or even just try 'cat
/dev/hpet'), it is
said, that device is busy. But jack has such option :/
I'm using kernel 2.6.33-rt. I can guess, that under rt kernel i should
not use HPET directly, because it is used by system,
and so, may be referred via 'system'. But even if that, such way could
bring some violations comparing to direct HPET usage.
May be indeed, HPET should be used directly only on non-rt systems?..
Btw, how i specified it: i have jack2 and ladish. Clock is specified
via ladiconf. Clock parameter type is integer; yesterday nedko showed
me a patch for jack, fixing this problem, where i saw order of
variants in enumeration (hpet variant is '2').
Jack's HPET support has an issue: /dev/hpet can only be opened a limited
number of times. When you use -c hpet, as well as Jack itself, each
client has /dev/hpet opened twice; once as an fd, and once as mmap. On
my systems /dev/hpet is limited to 3 or 4 opens, so this is practically
unusable for any Jack setup.
However you can tell the kernel to use HPET itself for the system clock:
echo hpet > /sys/devices/system/clocksource/clocksource0/current_clocksource
or put "clocksource=hpet" in your boot up command line.
And then -c system will use HPET, indirectly.
Peter.
9 Mar
9 Mar
5:52 p.m.
New subject: [LAU] Can't use HPET by JACK2 under kxstudio (probably, it is ubuntu problem too).
Thanks for reply. I tried again with generic, lowlatency and again - realtime kernels. It
seems, problem for jack is caused by utility jack2-simple-config, shiped in kxstudio.
There is forced restart function, which stupidly kills all daemons without any checks and
preparation (though it warns, what will happen, proposing to wait :). It seems, when
jackdbus is killed, hpet, probably, is not freed. Also when jack is started, 'lsof |
grep hpet' gives two jackdbus-related items. And if i try to start yoshimi or patchage
(using libjack, not dbus), they both try to use hpet... and fail :] . And also, runing
jack (i used ladish, because ladiconf has clock source option), in gladish i noticed, that
dsp load is equalk to some max... gladish showes dsp load in format <lower value>
(<high value (usually - up to 100%)>) e.g., 1.5% (100%); with HPET clock first value
was always same as second (growed from 75% up to 100%).
I added clocksource option to bootloader. Not sure yet, are there any changes (too hard to
check for me).
Tue, 08 Mar 2011 07:59:53 +0000 письмо от Peter Nelson <peter(a)fuzzle.org>rg>:
On Tue, 2011-03-08 at 09:57 +0300, Mike Cookson
wrote:
On attempt to use device (or even just try
'cat /dev/hpet'), it
is
said, that device is busy. But jack has such
option :/
I'm using kernel 2.6.33-rt. I can guess, that under rt kernel i
should
not use HPET directly, because it is used by
system,
and so, may be referred via 'system'. But even if that, such way
could
bring some violations comparing to direct HPET
usage.
May be indeed, HPET should be used directly only on non-rt systems?..
Btw, how i specified it: i have jack2 and ladish. Clock is specified
via ladiconf. Clock parameter type is integer; yesterday nedko showed
me a patch for jack, fixing this problem, where i saw order of
variants in enumeration (hpet variant is '2').
Jack's HPET support has an issue: /dev/hpet can only be opened a limited
number of times. When you use -c hpet, as well as Jack itself, each
client has /dev/hpet opened twice; once as an fd, and once as mmap. On
my systems /dev/hpet is limited to 3 or 4 opens, so this is practically
unusable for any Jack setup.
However you can tell the kernel to use HPET itself for the system clock:
echo hpet >
/sys/devices/system/clocksource/clocksource0/current_clocksource
or put "clocksource=hpet" in your boot up command line.
And then -c system will use HPET, indirectly.
Peter.
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6:06 p.m.
New subject: Can't use HPET by JACK2 under kxstudio (probably, it is ubuntu problem too).
On Wed, Mar 9, 2011 at 11:52 AM, Mike Cookson <cook60020tmp(a)mail.ru> wrote:
I added clocksource option to bootloader. Not sure
yet, are there any changes (too hard to check for me).
there will be no visible changes. using the HPET as a clocksource (in
JACK) is intended to guard against oddities caused by CPU frequency
scaling. if JACK uses the CPU instruction counter to check the passage
of wallclock time, its sense of time passing can be skewed by the CPU
being sped up and slowed down. there are no performance improvements
or behavioral changes expected from using the HPET instead.
i have no idea if using the HPET as the system (kernel) clocksource
offers the same protection.
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Paul Davis -
Peter Nelson