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my own malloc for psp

 
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Yoshihiro



Joined: 14 May 2005
Posts: 12
PostPosted: Sat Jun 04, 2005 1:02 am    Post subject: my own malloc for psp Reply with quote
hi i've make a malloc for psp that can be optimized it's jus for help :)

the c code :

Code:

/*
// PSP
Malloc(x) & Free() Yoshihiro

*/


#include <stdlib.h>
#include <errno.h>

#include <sys/types.h>
#include <unistd.h>
#include <stddef.h>
#include <stdarg.h>

int has_initialized = 0;

void *managed_memory_start;

void *last_valid_address;


struct mem_control_block {

   int is_available;

   int size;

};

typedef struct BLOCK {
  int size;
  struct BLOCK *next;
  int bucket;
} BLOCK;


char allocbuf[ALLOCSIZE];

char *allocp1 = allocbuf;

register char *stack_ptr asm ("$sp");
static char alloc_buffer[8*1024*1024];

caddr_t
_sbrk_psp (int incr)
{
/* defined */
  static char *heap_end = alloc_buffer;
  static int total;
  char *prev_heap_end;

  prev_heap_end = heap_end;
  if (heap_end + incr > stack_ptr)
    {
     abort ();
    }
  heap_end += incr;
  total += incr;
  return (caddr_t) prev_heap_end;
}

caddr_t sbrk_psp (int incr) { return _sbrk_psp(incr); }


void malloc_psp_init()

{

   last_valid_address = sbrk_psp(0);

   managed_memory_start = last_valid_address;

    has_initialized = 1;

}

void free_psp(void *firstbyte) {

   struct mem_control_block *mcb;


   mcb = firstbyte - sizeof(struct mem_control_block);

   mcb->is_available = 1;

   return;
}

void *malloc_psp(long numbytes) {

   void *current_location;


   struct mem_control_block *current_location_mcb;

   
   void *memory_location;

   
   if(! has_initialized)    {

      malloc_psp_init();

   }

   
   numbytes = numbytes + sizeof(struct mem_control_block);

   
   memory_location = 0;

   current_location = managed_memory_start;

   while(current_location != last_valid_address)

   {

      current_location_mcb =

         (struct mem_control_block *)current_location;

      if(current_location_mcb->is_available)

      {

         if(current_location_mcb->size >= numbytes)

         {

      
            current_location_mcb->is_available = 0;

            memory_location = current_location;

            break;

         }

      }

      current_location = current_location +

         current_location_mcb->size;

   }

   
   if(! memory_location)

   {

      sbrk_psp(numbytes);

      memory_location = last_valid_address;

   
      last_valid_address = last_valid_address + numbytes;

      current_location_mcb = memory_location;

      current_location_mcb->is_available = 0;

      current_location_mcb->size = numbytes;

   }

   
   memory_location = memory_location + sizeof(struct mem_control_block);

   
   return memory_location;

 }


void *
realloc(void *ptr, size_t size)
{
  BLOCK *b;
  char *newptr;
  int copysize;

  if (ptr == 0)
    return malloc_psp(size);

  b = (BLOCK *)((char *)ptr-4);
  copysize = b->size & ~1;
  if (size <= copysize)
  {
#if 0
    if (copysize < 2*MIN_SAVE_EXTRA
   || (size >= copysize-512 && size >= copysize/2))
#endif
      return ptr;
    copysize = size;
  }

  newptr = (char *)malloc_psp(size);

  memcpy(newptr, ptr, copysize);
  free_psp(ptr);
 

  return newptr;
}


the header for the cpp code :

Code:

extern "C"
{
void malloc_psp_init(void);

void free_psp(void *firstbyte);

void *malloc_psp(long numbytes);
}



friendly Yoshihiro
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Last edited by Yoshihiro on Mon Jun 06, 2005 9:58 am; edited 1 time in total
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subbie



Joined: 05 May 2005
Posts: 122
PostPosted: Sat Jun 04, 2005 4:29 am    Post subject: Reply with quote
cool.

Am I right in assuming that this line will effect how much we can allocate from? "static char alloc_buffer[8*1024*1024]; "

Also how is fragmentation. If we free all will we have access to the whole buffer size again or will it be broken into fragmented pieces?
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fcorbier



Joined: 25 Jun 2005
Posts: 1
PostPosted: Sat Jun 25, 2005 4:46 am    Post subject: Reply with quote
Hey Yoshihiro,

I'm using your malloc in my PSPRick project. It works fine but I made a small modification for it. I changed:

Code:
numbytes = numbytes + sizeof(struct mem_control_block);


to:

Code:
numbytes = ((numbytes+3)&~0x3) + sizeof(struct mem_control_block);


so that allocated memory are always 4-bytes aligned.

-fcorbier
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Agoln



Joined: 08 Jun 2005
Posts: 326
Location: Fort Wayne, IN
PostPosted: Sat Jun 25, 2005 5:27 am    Post subject: Reply with quote
fcorbier wrote:
so that allocated memory are always 4-bytes aligned.


Does MIPS need to be byte-aligned like SPARC?
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ector



Joined: 12 May 2005
Posts: 195
PostPosted: Sat Jun 25, 2005 6:10 am    Post subject: Reply with quote
Agoln wrote:

Does MIPS need to be byte-aligned like SPARC?


Yes.
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Agoln



Joined: 08 Jun 2005
Posts: 326
Location: Fort Wayne, IN
PostPosted: Sat Jun 25, 2005 6:29 am    Post subject: Reply with quote
Well, then thanks for the patch note for making it byte-aligned. I tried debugging a bus error for HOURS on end trying to figure out what was wrong before learning about byte-alignment and why I only got the errors on the SPARC machines.........

I HATE bus errors...
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Yoshihiro



Joined: 14 May 2005
Posts: 12
PostPosted: Mon Jun 27, 2005 8:06 am    Post subject: Reply with quote
fcorbier wrote:
Hey Yoshihiro,

I'm using your malloc in my PSPRick project. It works fine but I made a small modification for it. I changed:

Code:
numbytes = numbytes + sizeof(struct mem_control_block);


to:

Code:
numbytes = ((numbytes+3)&~0x3) + sizeof(struct mem_control_block);


so that allocated memory are always 4-bytes aligned.

-fcorbier


Thank's for your fix fcorbier :D.


..::Yoshihiro::..
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