RE: C400-L Digest, Vol 2, Issue 34 -- C400-L

You might try converting the malloc and free() functions to a User Space.
Create the user space in QTEMP, then get a pointer to it. The use the user
space as you would regular memory/storage. The user space will (optionally)
automatically extend as needed. I've found (in RPG IV at least) that the
User Space technique for dynamically sized arrays is no perceivable
difference in memory access and in realloc() comparisons seems faster. That
is the auto-extend feature seems to be faster than realloc().
-Bob Cozzi


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Subject: C400-L Digest, Vol 2, Issue 34

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Today's Topics:

   1. Porting C Linux to ILE C: Performance problem (Zvi Kave)
   2. RE: Porting C Linux to ILE C: Performance problem (Bob Crothers)


----------------------------------------------------------------------

message: 1
date: Wed, 30 Jun 2004 07:29:10 -0700 (PDT)
from: Zvi Kave <zvi_kave@xxxxxxxxx>
subject: [C400-L] Porting C Linux to ILE C: Performance problem

Dear collegues,

1. I ported succesfully(?) C coded software from Linux

   to ILE C. 
2. The sample program I use, takes in Linux 1 second.
   The same program run takes on the AS/400 ...
   7 minutes!?
3. When debugging the program on the AS/400, I found
   that the slow response is in the memory allocation
   routines, namely, calloc, malloc, realloc and 
   free().
   CPU usage is about 10%.
4. Those memory management routines are managed by
   linked list which is allocated in the beginning of
   program and free()d before end.

 Is there any reason for that performance problem?

  Please help.

  Regards,

   Zvi   

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------------------------------

message: 2
date: Wed, 30 Jun 2004 09:40:12 -0500
from: "Bob Crothers" <bob@xxxxxxxxxxxxxx>
subject: RE: [C400-L] Porting C Linux to ILE C: Performance problem

Realloc is always a poor performer as it needs to allocate a new block large
enough to fit the request, then copy the memory from the old location to the
new one and then return.

As a general rule, I try and limit the malloc's and free's that a program
uses as much as possible.  They tend to be expensive and make performance
very non-linear.  This is both AS/400 and Windows.  Havent done much
Linux/Unix work so I don't know about that.

Bob

> -----Original Message-----
> From: c400-l-bounces@xxxxxxxxxxxx [mailto:c400-l-bounces@xxxxxxxxxxxx] On
> Behalf Of Zvi Kave
> Sent: Wednesday, June 30, 2004 9:29 AM
> To: c400-l@xxxxxxxxxxxx
> Subject: [C400-L] Porting C Linux to ILE C: Performance problem
> 
> Dear collegues,
> 
> 1. I ported succesfully(?) C coded software from Linux
> 
>    to ILE C.
> 2. The sample program I use, takes in Linux 1 second.
>    The same program run takes on the AS/400 ...
>    7 minutes!?
> 3. When debugging the program on the AS/400, I found
>    that the slow response is in the memory allocation
>    routines, namely, calloc, malloc, realloc and
>    free().
>    CPU usage is about 10%.
> 4. Those memory management routines are managed by
>    linked list which is allocated in the beginning of
>    program and free()d before end.
> 
>  Is there any reason for that performance problem?
> 
>   Please help.
> 
>   Regards,
> 
>    Zvi
> 
> __________________________________________________
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> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
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End of C400-L Digest, Vol 2, Issue 34
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