Subject: [linux-audio-dev] low-latency news: preemptive kernel, preemptive-2.3.52-B7
From: Benno Senoner (sbenno_AT_gardena.net)
Date: Wed Mar 15 2000 - 08:14:47 EST
forwarding news from Roger Larsson,
Roger that stuff looks interesting,
can you please enlighten us on the linux-audio-dev list,
which advantages the new approach has ?
Anyway I will benchmark this 2.3.52-B7 kernel to see how it compares
to the old stuff.
Roger, can you post the URL of the 2.2.15 lowlatency patch ?
Benno.
On Wed, 15 Mar 2000, Roger Larsson wrote:
> Hi again Benno,
>
> Have you seen the newest stuff from Ingo.
> It is a new approach!
>
> Where you mark kernel code as preemtive, like:
> unsigned int csum_partial_copy( const char *src, char *dst, int len,
> int sum);
> preempt_on();
> ret = csum_partial_copy_generic ( src, dst, len, sum, err_ptr, NULL);
> preempt_off();
> return ret;
> }
> (The 'preempt_on' does a conditional_reshedule too!)
>
> /RogerL
>
> PS
> Ingo has released a lowlatency for 2.2.15 recently.
> DS
>
> Ingo Molnar wrote:
> >
> > This is the latest preemptive-kernel patch:
> >
> > http://www.redhat.com/~mingo/preemptive-kernel/preemptive-2.3.52-B7
> >
> > (also attached) Changes since A7:
> >
> > - wrappers: preempt_on() and preempt_off().
> >
> > - more places marked preemptable:
> >
> > - all the user-copy functions in usercopy.c
> > - user-checksumming functions in checksum.S
> > - some highmem places which are safe
> > - those buffer.c 'buffer clearing' places which can be
> > rescheduled
> >
> > - fixed a bug in random.c: it was doing a copy_user with
> > TASK_INTERRUPTIBLE - this can cause stuck processes.
> >
> > - similar bug in n_tty.c: memcpy_from_user done with
> > TASK_INTERRUPTIBLE.
> >
> > - (added a temporary assert to filter out bugs like those above)
> >
> > - (removed checksum-old.c and old references from x86, nothing was
> > using it anymore)
> >
> > - patch against pre3-2.3.52
> >
> > The kernel is rock solid here under load (SMP).
> >
> > Ingo
> >
> > ------------------------------------------------------------------------
> > Name: preemptive-2.3.52-B7
> > preemptive-2.3.52-B7 Type: Plain Text (TEXT/PLAIN)
> > Encoding: BASE64
>
> --
> Home page:
> http://www.norran.net/nra02596/
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