diff options
Diffstat (limited to 'Src')
| -rw-r--r-- | Src/mem.c | 153 |
1 files changed, 114 insertions, 39 deletions
diff --git a/Src/mem.c b/Src/mem.c index 027c35d9c..0a9665d09 100644 --- a/Src/mem.c +++ b/Src/mem.c @@ -64,6 +64,15 @@ guarantees that the memory for the pool is at the end of the memory which means that we can give it back to the system when the pool is freed. + + hrealloc(char *p, size_t old, size_t new) is an optimisation + with a similar interface to realloc(). Typically the new size + will be larger than the old one, since there is no gain in + shrinking the allocation (indeed, that will confused hrealloc() + since it will forget that the unused space once belonged to this + pointer). However, new == 0 is a special case; then if we + had to allocate a special heap for this memory it is freed at + that point. */ #if defined(HAVE_SYS_MMAN_H) && defined(HAVE_MMAP) && defined(HAVE_MUNMAP) @@ -98,9 +107,13 @@ union mem_align { #define H_ISIZE sizeof(union mem_align) #define HEAPSIZE (16384 - H_ISIZE) +/* Memory available for user data in default arena size */ #define HEAP_ARENA_SIZE (HEAPSIZE - sizeof(struct heap)) #define HEAPFREE (16384 - H_ISIZE) +/* Memory available for user data in heap h */ +#define ARENA_SIZEOF(h) ((h)->size - sizeof(struct heap)) + /* list of zsh heaps */ static Heap heaps; @@ -215,7 +228,7 @@ freeheap(void) memset(arena(h) + h->sp->used, 0xff, h->used - h->sp->used); #endif h->used = h->sp->used; - if (!fheap && h->used < HEAP_ARENA_SIZE) + if (!fheap && h->used < ARENA_SIZEOF(h)) fheap = h; hl = h; } else { @@ -258,7 +271,7 @@ popheap(void) memset(arena(h) + hs->used, 0xff, h->used - hs->used); #endif h->used = hs->used; - if (!fheap && h->used < HEAP_ARENA_SIZE) + if (!fheap && h->used < ARENA_SIZEOF(h)) fheap = h; zfree(hs, sizeof(*hs)); @@ -279,6 +292,44 @@ popheap(void) unqueue_signals(); } +#ifdef USE_MMAP +/* + * Utility function to allocate a heap area of at least *n bytes. + * *n will be rounded up to the next page boundary. + */ +static Heap +mmap_heap_alloc(size_t *n) +{ + Heap h; + static size_t pgsz = 0; + + if (!pgsz) { + +#ifdef _SC_PAGESIZE + pgsz = sysconf(_SC_PAGESIZE); /* SVR4 */ +#else +# ifdef _SC_PAGE_SIZE + pgsz = sysconf(_SC_PAGE_SIZE); /* HPUX */ +# else + pgsz = getpagesize(); +# endif +#endif + + pgsz--; + } + *n = (*n + pgsz) & ~pgsz; + h = (Heap) mmap(NULL, *n, PROT_READ | PROT_WRITE, + MMAP_FLAGS, -1, 0); + if (h == ((Heap) -1)) { + zerr("fatal error: out of heap memory", NULL, 0); + exit(1); + } + + return h; +} +#endif + + /* allocate memory from the current memory pool */ /**/ @@ -298,9 +349,10 @@ zhalloc(size_t size) /* find a heap with enough free space */ - for (h = ((fheap && HEAP_ARENA_SIZE >= (size + fheap->used)) ? fheap : heaps); + for (h = ((fheap && ARENA_SIZEOF(fheap) >= (size + fheap->used)) + ? fheap : heaps); h; h = h->next) { - if (HEAP_ARENA_SIZE >= (n = size + h->used)) { + if (ARENA_SIZEOF(h) >= (n = size + h->used)) { void *ret; h->used = n; @@ -322,32 +374,7 @@ zhalloc(size_t size) for (hp = NULL, h = heaps; h; hp = h, h = h->next); #ifdef USE_MMAP - { - static size_t pgsz = 0; - - if (!pgsz) { - -#ifdef _SC_PAGESIZE - pgsz = sysconf(_SC_PAGESIZE); /* SVR4 */ -#else -# ifdef _SC_PAGE_SIZE - pgsz = sysconf(_SC_PAGE_SIZE); /* HPUX */ -# else - pgsz = getpagesize(); -# endif -#endif - - pgsz--; - } - n = (n + pgsz) & ~pgsz; - h = (Heap) mmap(NULL, n, PROT_READ | PROT_WRITE, - MMAP_FLAGS, -1, 0); - if (h == ((Heap) -1)) { - zerr("fatal error: out of heap memory", NULL, 0); - exit(1); - } - h->size = n; - } + h = mmap_heap_alloc(&n); #else h = (Heap) zalloc(n); #endif @@ -358,6 +385,7 @@ zhalloc(size_t size) called = 1; #endif + h->size = n; h->used = size; h->next = NULL; h->sp = NULL; @@ -391,13 +419,21 @@ hrealloc(char *p, size_t old, size_t new) queue_signals(); for (h = heaps, ph = NULL; h; ph = h, h = h->next) - if (p >= arena(h) && p < arena(h) + HEAP_ARENA_SIZE) + if (p >= arena(h) && p < arena(h) + ARENA_SIZEOF(h)) break; DPUTS(!h, "BUG: hrealloc() called for non-heap memory."); DPUTS(h->sp && arena(h) + h->sp->used > p, "BUG: hrealloc() wants to realloc pushed memory"); + /* + * If the end of the old chunk is before the used pointer, + * more memory has been zhalloc'ed afterwards. + * We can't tell if that's still in use, obviously, since + * that's the whole point of heap memory. + * We have no choice other than to grab some more memory + * somewhere else and copy in the old stuff. + */ if (p + old < arena(h) + h->used) { if (new > old) { char *ptr = (char *) zhalloc(new); @@ -415,7 +451,19 @@ hrealloc(char *p, size_t old, size_t new) DPUTS(p + old != arena(h) + h->used, "BUG: hrealloc more than allocated"); + /* + * We now know there's nothing afterwards in the heap, now see if + * there's nothing before. Then we can reallocate the whole thing. + * Otherwise, we need to keep the stuff at the start of the heap, + * then allocate a new one too; this is handled below. (This will + * guarantee we occupy a full heap next time round, provided we + * don't use the heap for anything else.) + */ if (p == arena(h)) { + /* + * Zero new seems to be a special case saying we've finished + * with the specially reallocated memory, see scanner() in glob.c. + */ if (!new) { if (ph) ph->next = h->next; @@ -430,24 +478,51 @@ hrealloc(char *p, size_t old, size_t new) unqueue_signals(); return NULL; } -#ifndef USE_MMAP - if (old > HEAP_ARENA_SIZE || new > HEAP_ARENA_SIZE) { - size_t n = HEAP_ARENA_SIZE > new ? HEAPSIZE : new + sizeof(*h); + if (new > ARENA_SIZEOF(h)) { + /* + * Not enough memory in this heap. Allocate a new + * one of sufficient size. + * + * To avoid this happening too often, allocate + * chunks in multiples of HEAPSIZE. + * (Historical note: there didn't used to be any + * point in this since we didn't consistently record + * the allocated size of the heap, but now we do.) + */ + size_t n = (new + sizeof(*h) + HEAPSIZE); + n -= n % HEAPSIZE; +#ifdef USE_MMAP + /* + * I don't know any easy portable way of requesting + * a mmap'd segment be extended, so simply allocate + * a new one and copy. + */ + Heap hnew; + + hnew = mmap_heap_alloc(&n); + /* Copy the entire heap, header (with next pointer) included */ + memcpy(hnew, h, h->size); + munmap((void *)h, h->size); + h = hnew; +#else + h = (Heap) realloc(h, n); +#endif + + h->size = n; if (ph) - ph->next = h = (Heap) realloc(h, n); + ph->next = h; else - heaps = h = (Heap) realloc(h, n); + heaps = h; } h->used = new; unqueue_signals(); return arena(h); -#endif } #ifndef USE_MMAP - DPUTS(h->used > HEAP_ARENA_SIZE, "BUG: hrealloc at invalid address"); + DPUTS(h->used > ARENA_SIZEOF(h), "BUG: hrealloc at invalid address"); #endif - if (h->used + (new - old) <= HEAP_ARENA_SIZE) { + if (h->used + (new - old) <= ARENA_SIZEOF(h)) { h->used += new - old; unqueue_signals(); return p; |