kmalloc.c

#include <defs.h>
#include <list.h>
#include <memlayout.h>
#include <assert.h>
#include <kmalloc.h>
#include <sync.h>
#include <pmm.h>
#include <stdio.h>

/*
 * SLOB Allocator: Simple List Of Blocks
 *
 * Matt Mackall <[e-mail]> 12/30/03
 *
 * How SLOB works:
 *
 * The core of SLOB is a traditional K&R style heap allocator, with
 * support for returning aligned objects. The granularity of this
 * allocator is 8 bytes on x86, though it's perhaps possible to reduce
 * this to 4 if it's deemed worth the effort. The slob heap is a
 * singly-linked list of pages from __get_free_page, grown on demand
 * and allocation from the heap is currently first-fit.
 *
 * Above this is an implementation of kmalloc/kfree. Blocks returned
 * from kmalloc are 8-byte aligned and prepended with a 8-byte header.
 * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
 * __get_free_pages directly so that it can return page-aligned blocks
 * and keeps a linked list of such pages and their orders. These
 * objects are detected in kfree() by their page alignment.
 *
 * SLAB is emulated on top of SLOB by simply calling constructors and
 * destructors for every SLAB allocation. Objects are returned with
 * the 8-byte alignment unless the SLAB_MUST_HWCACHE_ALIGN flag is
 * set, in which case the low-level allocator will fragment blocks to
 * create the proper alignment. Again, objects of page-size or greater
 * are allocated by calling __get_free_pages. As SLAB objects know
 * their size, no separate size bookkeeping is necessary and there is
 * essentially no allocation space overhead.
 */


//some helper
#define spin_lock_irqsave(l, f) local_intr_save(f)
#define spin_unlock_irqrestore(l, f) local_intr_restore(f)
typedef unsigned int gfp_t;
#ifndef PAGE_SIZE
#define PAGE_SIZE PGSIZE
#endif

#ifndef L1_CACHE_BYTES
#define L1_CACHE_BYTES 64
#endif

#ifndef ALIGN
#define ALIGN(addr,size)   (((addr)+(size)-1)&(~((size)-1))) 
#endif


struct slob_block {
    int units;
    struct slob_block *next;
};
typedef struct slob_block slob_t;

#define SLOB_UNIT sizeof(slob_t)
#define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
#define SLOB_ALIGN L1_CACHE_BYTES

struct bigblock {
    int order;
    void *pages;
    struct bigblock *next;
};
typedef struct bigblock bigblock_t;

static slob_t arena = { .next = &arena, .units = 1 };
static slob_t *slobfree = &arena;
static bigblock_t *bigblocks;


static void* __slob_get_free_pages(gfp_t gfp, int order)
{
  struct Page * page = alloc_pages(1 << order);
  if(!page)
    return NULL;
  return page2kva(page);
}

#define __slob_get_free_page(gfp) __slob_get_free_pages(gfp, 0)

static inline void __slob_free_pages(unsigned long kva, int order)
{
  free_pages(kva2page(kva), 1 << order);
}

static void slob_free(void *b, int size);

static void *slob_alloc(size_t size, gfp_t gfp, int align)
{
  assert( (size + SLOB_UNIT) < PAGE_SIZE );

    slob_t *prev, *cur, *aligned = 0;
    int delta = 0, units = SLOB_UNITS(size);
    unsigned long flags;

    spin_lock_irqsave(&slob_lock, flags);
    prev = slobfree;
    for (cur = prev->next; ; prev = cur, cur = cur->next) {
        if (align) {
            aligned = (slob_t *)ALIGN((unsigned long)cur, align);
            delta = aligned - cur;
        }
        if (cur->units >= units + delta) { /* room enough? */
            if (delta) { /* need to fragment head to align? */
                aligned->units = cur->units - delta;
                aligned->next = cur->next;
                cur->next = aligned;
                cur->units = delta;
                prev = cur;
                cur = aligned;
            }

            if (cur->units == units) /* exact fit? */
                prev->next = cur->next; /* unlink */
            else { /* fragment */
                prev->next = cur + units;
                prev->next->units = cur->units - units;
                prev->next->next = cur->next;
                cur->units = units;
            }

            slobfree = prev;
            spin_unlock_irqrestore(&slob_lock, flags);
            return cur;
        }
        if (cur == slobfree) {
            spin_unlock_irqrestore(&slob_lock, flags);

            if (size == PAGE_SIZE) /* trying to shrink arena? */
                return 0;

            cur = (slob_t *)__slob_get_free_page(gfp);
            if (!cur)
                return 0;

            slob_free(cur, PAGE_SIZE);
            spin_lock_irqsave(&slob_lock, flags);
            cur = slobfree;
        }
    }
}

static void slob_free(void *block, int size)
{
    slob_t *cur, *b = (slob_t *)block;
    unsigned long flags;

    if (!block)
        return;

    if (size)
        b->units = SLOB_UNITS(size);

    /* Find reinsertion point */
    spin_lock_irqsave(&slob_lock, flags);
    for (cur = slobfree; !(b > cur && b < cur->next); cur = cur->next)
        if (cur >= cur->next && (b > cur || b < cur->next))
            break;

    if (b + b->units == cur->next) {
        b->units += cur->next->units;
        b->next = cur->next->next;
    } else
        b->next = cur->next;

    if (cur + cur->units == b) {
        cur->units += b->units;
        cur->next = b->next;
    } else
        cur->next = b;

    slobfree = cur;

    spin_unlock_irqrestore(&slob_lock, flags);
}



void check_slab(void) {
  cprintf("check_slab() success\n");
}

void
slab_init(void) {
  cprintf("use SLOB allocator\n");
  check_slab();
}

inline void 
kmalloc_init(void) {
    slab_init();
    cprintf("kmalloc_init() succeeded!\n");
}

size_t
slab_allocated(void) {
  return 0;
}

size_t
kallocated(void) {
   return slab_allocated();
}

static int find_order(int size)
{
    int order = 0;
    for ( ; size > 4096 ; size >>=1)
        order++;
    return order;
}

static void *__kmalloc(size_t size, gfp_t gfp)
{
    slob_t *m;
    bigblock_t *bb;
    unsigned long flags;

    if (size < PAGE_SIZE - SLOB_UNIT) {
        m = slob_alloc(size + SLOB_UNIT, gfp, 0);
        return m ? (void *)(m + 1) : 0;
    }

    bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
    if (!bb)
        return 0;

    bb->order = find_order(size);
    bb->pages = (void *)__slob_get_free_pages(gfp, bb->order);

    if (bb->pages) {
        spin_lock_irqsave(&block_lock, flags);
        bb->next = bigblocks;
        bigblocks = bb;
        spin_unlock_irqrestore(&block_lock, flags);
        return bb->pages;
    }

    slob_free(bb, sizeof(bigblock_t));
    return 0;
}

void *
kmalloc(size_t size)
{
  return __kmalloc(size, 0);
}


void kfree(void *block)
{
    bigblock_t *bb, **last = &bigblocks;
    unsigned long flags;

    if (!block)
        return;

    if (!((unsigned long)block & (PAGE_SIZE-1))) {
        /* might be on the big block list */
        spin_lock_irqsave(&block_lock, flags);
        for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {
            if (bb->pages == block) {
                *last = bb->next;
                spin_unlock_irqrestore(&block_lock, flags);
                __slob_free_pages((unsigned long)block, bb->order);
                slob_free(bb, sizeof(bigblock_t));
                return;
            }
        }
        spin_unlock_irqrestore(&block_lock, flags);
    }

    slob_free((slob_t *)block - 1, 0);
    return;
}


unsigned int ksize(const void *block)
{
    bigblock_t *bb;
    unsigned long flags;

    if (!block)
        return 0;

    if (!((unsigned long)block & (PAGE_SIZE-1))) {
        spin_lock_irqsave(&block_lock, flags);
        for (bb = bigblocks; bb; bb = bb->next)
            if (bb->pages == block) {
                spin_unlock_irqrestore(&slob_lock, flags);
                return PAGE_SIZE << bb->order;
            }
        spin_unlock_irqrestore(&block_lock, flags);
    }

    return ((slob_t *)block - 1)->units * SLOB_UNIT;
}