I'm using not so much RAM, at compile time is around 1700 bytes (it depends on
the different versions of my program).
But now, after other tests, i see that when the motes enter in the
reading-from-flash phase, something happens and some of them break down. They
are not more able to work.And only after a reading phase.
May be the batteries? i know about the 70mA of current, but if i use
rechangeable batteries, so 1.3 V, are there problems?i can measure only voltage
by a voltmetre.
I really don't know how to understand what's going on in the reading phase to
let some motes to break down in this way.
One problem may be is about the parameters i need when the reading phase is
done: i need the same parameters i use when i posted the task.So the global
parameters buf_flash,State,mess,flashAddr,
flashLen,flashBuffer are probably different when the readDone event fires up
from the ones used posting the task.But only when the reading is done i can use
that buffer and so i can execute my program..so for example sending
packets,math operations,etc..
Buffer *flashBuffer,*buffer,*ibuf,*ibuff;
Buf_flash *Head,*buf_flash;
Datagram *mess,*datagram;
uint8_t State;
task void readFlash(){
if (!call FlashBridge.read(flashAddr,flashBuffer,flashLen)){
post readFlash();}
return;
}
void readInToFlash(uint8_t s,Buf_flash *buf,Datagram *message,Buffer
*buffer_r,uint32_t addr, uint32_t len){
buf_flash=buf;
State=s;
mess=message;
flashAddr=addr;
flashLen=len;
flashBuffer=buffer_r;
post readFlash();
return;
}
event void FlashBridge.readDone(uint32_t addr, void *buf, uint32_t len,
result_t result){
if (result){
//operations where i need to use the same global variables declared in the
task!for now i'm using normally mess,State,etc..but i think are different from
the same one before posting the task.
//for example if i use
//if(mess->data==...).....
//i think it is not the same "mess" written before "post readFlash()"...
else
post readFlash();
return;
}
-----Original Message-----
From: David Moss [mailto:[EMAIL PROTECTED]
Sent: Fri 9/15/2006 6:27 PM
To: Munaretto, Daniel; [email protected]
Cc:
Subject: RE: [Tinyos-help] repeating tests,no free memory
How much RAM is your program consuming at compile time? The MicaZ is
notorious for running out of RAM just when you need it because it only
has
4kB. If your global memory usage is already quite a bit (3kB maybe?
maybe
more? maybe less?) and you throw a bunch of stuff on the stack, your
mote
will crash in a seemingly random fashion, depending on what's going on.
I've had apps before that used around 3kB of RAM when the program is
compiled, and then crashed awhile later because the stack overflowed.
If the task queue is full (and it's in global memory btw, so simply
posting
tasks shouldn't cause a stack overflow) then when you post a task, the
post
will return FAIL. It could also be that your app is posting a task and
expecting it to run before continuing on, and that task never actually
got
posted. I've personally never had that problem before, even with
running a
full file system on top of flash bridge with the radio transmitting and
receiving.
-----Original Message-----
From: Munaretto, Daniel [mailto:[EMAIL PROTECTED]
Sent: Friday, September 15, 2006 9:02 AM
To: David Moss; [email protected]
Subject: RE: [Tinyos-help] repeating tests,no free memory
Dear all,
i tried to use TinyAlloc interface but the results are really
similar.
So this is not a problem of the calloc function.
But i start thinking the problem is in the stack. If i post too many
tasks,
can the mote crash?
The problem is that i have to use tasks to handle the FlashBridge
interface
in order to use properly the reading and writing phase on Flash-RAM.
And i'm
also using a task for the sending interface (own mote messages) and for
the
forwarding one (messages from other motes), all synchronized by timers.
So if i use micaz motes, tinyos-1.x, can it be a problem?
Because i'm freeing all the times the memory i allocate, but if i
repeat the
experiments with the motes on, in the second round or in the third one,
one
(or more)of these breaks down. It seems quite randomly.
Hoping in any kind of help,
cheers
Daniele
-----Original Message-----
From: David Moss [mailto:[EMAIL PROTECTED]
Sent: Mon 9/11/2006 7:56 PM
To: Munaretto, Daniel; [email protected]
Cc:
Subject: RE: [Tinyos-help] repeating tests,no free memory
Daniele,
This was one thing I noticed about the code I looked at but
failed
to warn
against, because I didn't know any better until I read up on it
afterwards.
Below are a few emails from this list that may point you in the
right
direction.
-David
https://mail.millennium.berkeley.edu/pipermail/tinyos-help/2005-February/007
712.html :
"The TinyOS programming methodology frowns on malloc, for
several
reasons:
1) No memory protection so you can smash your stack
2) Unforeseen rate mismatches can cause you to do 1 (you start
receiving packets faster than you can forward them)
3) Event-driven execution models can make free()ing a hard
thing to
do
right (hence pool allocations, etc.)
If you want dynamic allocation, look at TinyAlloc (which Joe
mentioned). It allows you to allocate a static chunk of RAM
which
you
then parcel out dynamically. But using it in the presence of
conflicting components is a recipe for disaster. Systems such
as
TinyDB
get away with it because all their parts are designed to work
together.
Phil"
"Hi all,
Refer to the paper "The NesC Language: A Holistic
Approach to
Networked Embedded Systems", dynamic memory allocation and
function
pointers are prohibited in NesC language. For dynamic memory
allocation, it's quite clear to me why we can't use it in
TinyOS as
refered to
https://mail.millennium.berkeley.edu/pipermail/tinyos-help/2005-February/007
712.html
. We can use TinyAlloc or MemAlloc instead of directly calling
malloc() and so on. But for function pointers, it's not clear
to me
that we can or can't use it in TinyOS. What would be the
problems if
I
use that?"
"Short answer: it leads to more reliable code.
Long answer:
Here's a pointer (haha!):
http://mail.millennium.berkeley.edu/pipermail/tinyos-help/2005-February/0077
12.html
There's a difference between malloc() and dynamic allocation.
nesC
does not forbid dynamic memory allocation: there's nothing
stopping
you from writing a component that allocates a pool of memory
and has
dynamic allocation interfaces. Take a look at TinyAlloc, for
example.
nesC does, however, frown on malloc, for the reasons described
in
the
above mail. Modern coding styles generally assume unbounded
memory,
in as much that you have swap space so will see tremendous
performance degradation before the system crashes. General
application behavior on allocation failure is to exit(2) and
therefore deallocate everything. With a processes,
multitasking, and
automatic page reclamation, this works fine. But on an embedded
system with no memory protection, well, it's not so clean.
Part of the issue is that while dynamic allocation among a set
of
cooperating components can work fine (e.g., TinyDB, Ben
Greenstein
@UCLA's work on signal processing), dynamic allocation between
arbitrary components (a single shared pool) is a recipe for
disaster.
One bad component can bring the entire system down, as the
shared
resource breaks inter-component isolation.
The reason why nesC frowns on function pointers is because they
are
dangerous and except for a few edge cases (e.g., dynamically
linking
new binary modules), unnecessary. You know the call graph at
compile-
time. Instead of storing a function pointer in memory, which
could
be
corrupted and lead you to jump to certain doom, you can just
use a
parameterized interface and call based on a function ID. This
also
gives you type checking for the functions It is more robust,
just as
easy (once you get used to it), and generally uses less RAM (no
need
to store the pointer). Function pointers are a basic result of
C's
linking model. nesC's linking model does not have the same
complications (interfaces are bidirectional), so you can avoid
them.
Phil"
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Munaretto,
Daniel
Sent: Monday, September 11, 2006 1:51 AM
To: [email protected]
Subject: [Tinyos-help] repeating tests,no free memory
Dear all,
i discover a really strange behavior in my application.
I repeat more times my code, and after some experiments the
motes
break
down.
So there is a memory problem.
But i'm sure i free all the memory i allocate during the code.
I'm
using
only a buffer and i re-use it all the times, instead i allocate
memory with
"calloc()" only for creating a chain which i delete at the end
of
each
simulation with the "free" command and then i give "NULL" to
the
pointers.
So i don't understand where i lose memory each time i re-run
the
program
(without re-booting the motes). i'm in tinyos 1.1.15,micaz
motes.
I'm using the FlashBridge interface because i'm working on the
flash.
I'm supposing that, may be, the problem is in the way Tinyos
handles
the
packets received. For example, in the function "event
TOS_MsgPtr
Receive.receive(TOS_MsgPtr m)", before returning m, do i have
to
free it?But
i can see it's wrong to do..
Please, if anyone knows where i have to find the waste of
memory
(may be
some interfaces)...any helps will be really appreciated
thanks very much
cheers
Daniele
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