enabling/disabling trampoline

Cristiano Ligieri Pereira cpereira at ics.uci.edu
Thu Mar 13 21:00:51 CET 2003

I'm not managing to get hazelnut working properly. It boots but then when
it creates the Linux panics with the following messages:

Kernel panic: failed to create ping pong task
In swapper task = no syncing
--- Linux panic ---

Might be something stupid but I can't figure it out.
Any suggestion?


Cristiano Ligieri Pereira - http://www.ics.uci.edu/~cpereira

> Of course(!) Hazelnut works fine with Pentium 4 machines.  Even though
> our (the group in Karlsruhe) focus is now on developing the Pistachio
> kernel, the Hazelnut kernel is definitely not something to frown upon.
> It is more than stable enough to do a decent job (at least for
> benchmarking puposes).  We've even been running our web server on top
> of L4Linux/Hazelnut for several months.
> The Dresden people will probably kill me for saying so :-), but if you
> want to do performance measurements (except for measurments concerning
> real-time workloads, e.g., interrupt latency), you should definitely
> go for the Hazelnut kernel.
> I can't seem to remember what the performance numbers for the original
> asm kernel is on the Pentium 4, but for Pentium III the Hazelnut
> kernel was actually performing slightly better than the original asm
> kernel.  (This only goes for pure IPC times.  I don't have other
> metrics like cache footprint, etc., at hand.)  The reason why Hazelnut
> was performing better was that it was optimized with the newer Pentium
> III (and Pentium 4) chips in mind, whereas the asm kernel had not been
> updated to take advantage of the newer CPU architectures.  You can
> therefore expect the difference to be even larger for Pentium 4.
> Another reason why you might want to use Hazelnut for performance
> measurements is that it supports small spaces (emulation of tagged
> TLBs).  The impertance of having small spaces has increased with the
> years since the TLBs have gotten larger, hence impose a larger
> indirect penalty when they are flushed; and the TLB miss penalty has
> gotten higher due to longer pipelines and a greater disparity between
> CPU speed and memory access speed.  In addition, the Pentium 4 also
> contains a 12K u-ops Trace Cache (i.e., an instruction cache) which is
> virtually tagged and therefore flushed on cr3 reloads (address space
> switches).  Having small spaces also avoids such trace cache flushes.
> As an example of the benefit of small spaces, an L4Linux getpid()
> syscall is 70% slower on a kernel without small spaces compared to a
> kernel with small spaces enabled [1].
> When compiling Hazelnut to run you benchmarks remember to turn of
> tracepoints, IPC tracing, spin wheels, etc., and make sure that the
> FastPath IPC and small spaces are enabled.  This can all be done using
> make (x)config.
> 	eSk
> [1] http://i30www.ira.uka.de/research/documents/l4ka/smallspaces.pdf
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