Re: migration thread and active_load_balance

[Dmitry Adamushko]

On 20/04/2008, Dan Upton <upton.dan.linux@xxxxxxxxx> wrote:
> Back again with more questions about the scheduler, as I've spent two
>  or three days trying to debug on my own and I'm just not getting
>  anywhere.
>
>  Basically, I'm trying to add a new active balancing mechanism.  I made
>  out a diagram of how migration_thread  calls active_load_balance and
>  so on, and I use a flag (set by writing to a file in sysfs) to
>  determine whether to use the standard iterator for the CFS runqueue or
>  a different iterator I wrote.  The new iterator seems to work fine, as
>  I've been using it (again, with a flag) to replace the regular
>  iterator when it's called from schedule by idle_balance.  I basically
>  tried adding an extra conditional in migration_thread that sets up
>  some state and then calls active_load_balance, but I was getting
>  deadlocks.  I'm not really sure why, since all I've really changed is
>  add a few variables to struct rq and struct cfs_rq.
>
>  I tried only doing my state setup and restore in that conditional,
>  without actually calling active_load_balance, which has given me an
>  even more frustrating result--the kernel does not deadlock, but it
>  does seem to crash in such a manner as to require a hard reset of the
>  machine.  (For instance, at one point I got an "invalid page state in
>  process 'init'" message from the kernel; if I try to reboot from Gnome
>  though it hangs.)  I don't understand this at all, since as far as I
>  can tell I'm using thread-local variables and really all I'm doing
>  right now is assignments to them.  Unless, of course the struct rq
>  (from rq = cpu_rq(cpu);) could be being manipulated elsewhere, leading
>  to some sort of race condition...
>

can you post your modifications? I'd be much more easy to see what you
are doing...

thanks in advance.


>
>  Thanks,
>  -dan
>

-- 
Best regards,
Dmitry Adamushko
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