1 files changed, 387 insertions, 0 deletions
diff --git a/src/malloc/mallocng/malloc.c b/src/malloc/mallocng/malloc.c
new file mode 100644
index 00000000..d695ab8e
--- /dev/null
+++ b/src/malloc/mallocng/malloc.c
@@ -0,0 +1,387 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <limits.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <errno.h>
+
+#include "meta.h"
+
+LOCK_OBJ_DEF;
+
+const uint16_t size_classes[] = {
+	1, 2, 3, 4, 5, 6, 7, 8,
+	9, 10, 12, 15,
+	18, 20, 25, 31,
+	36, 42, 50, 63,
+	72, 84, 102, 127,
+	146, 170, 204, 255,
+	292, 340, 409, 511,
+	584, 682, 818, 1023,
+	1169, 1364, 1637, 2047,
+	2340, 2730, 3276, 4095,
+	4680, 5460, 6552, 8191,
+};
+
+static const uint8_t small_cnt_tab[][3] = {
+	{ 30, 30, 30 },
+	{ 31, 15, 15 },
+	{ 20, 10, 10 },
+	{ 31, 15, 7 },
+	{ 25, 12, 6 },
+	{ 21, 10, 5 },
+	{ 18, 8, 4 },
+	{ 31, 15, 7 },
+	{ 28, 14, 6 },
+};
+
+static const uint8_t med_cnt_tab[4] = { 28, 24, 20, 32 };
+
+struct malloc_context ctx = { 0 };
+
+struct meta *alloc_meta(void)
+{
+	struct meta *m;
+	unsigned char *p;
+	if (!ctx.init_done) {
+#ifndef PAGESIZE
+		ctx.pagesize = get_page_size();
+#endif
+		ctx.secret = get_random_secret();
+		ctx.init_done = 1;
+	}
+	size_t pagesize = PGSZ;
+	if (pagesize < 4096) pagesize = 4096;
+	if ((m = dequeue_head(&ctx.free_meta_head))) return m;
+	if (!ctx.avail_meta_count) {
+		int need_unprotect = 1;
+		if (!ctx.avail_meta_area_count && ctx.brk!=-1) {
+			uintptr_t new = ctx.brk + pagesize;
+			int need_guard = 0;
+			if (!ctx.brk) {
+				need_guard = 1;
+				ctx.brk = brk(0);
+				// some ancient kernels returned _ebss
+				// instead of next page as initial brk.
+				ctx.brk += -ctx.brk & (pagesize-1);
+				new = ctx.brk + 2*pagesize;
+			}
+			if (brk(new) != new) {
+				ctx.brk = -1;
+			} else {
+				if (need_guard) mmap((void *)ctx.brk, pagesize,
+					PROT_NONE, MAP_ANON|MAP_PRIVATE|MAP_FIXED, -1, 0);
+				ctx.brk = new;
+				ctx.avail_meta_areas = (void *)(new - pagesize);
+				ctx.avail_meta_area_count = pagesize>>12;
+				need_unprotect = 0;
+			}
+		}
+		if (!ctx.avail_meta_area_count) {
+			size_t n = 2UL << ctx.meta_alloc_shift;
+			p = mmap(0, n*pagesize, PROT_NONE,
+				MAP_PRIVATE|MAP_ANON, -1, 0);
+			if (p==MAP_FAILED) return 0;
+			ctx.avail_meta_areas = p + pagesize;
+			ctx.avail_meta_area_count = (n-1)*(pagesize>>12);
+			ctx.meta_alloc_shift++;
+		}
+		p = ctx.avail_meta_areas;
+		if ((uintptr_t)p & (pagesize-1)) need_unprotect = 0;
+		if (need_unprotect)
+			if (mprotect(p, pagesize, PROT_READ|PROT_WRITE)
+			    && errno != ENOSYS)
+				return 0;
+		ctx.avail_meta_area_count--;
+		ctx.avail_meta_areas = p + 4096;
+		if (ctx.meta_area_tail) {
+			ctx.meta_area_tail->next = (void *)p;
+		} else {
+			ctx.meta_area_head = (void *)p;
+		}
+		ctx.meta_area_tail = (void *)p;
+		ctx.meta_area_tail->check = ctx.secret;
+		ctx.avail_meta_count = ctx.meta_area_tail->nslots
+			= (4096-sizeof(struct meta_area))/sizeof *m;
+		ctx.avail_meta = ctx.meta_area_tail->slots;
+	}
+	ctx.avail_meta_count--;
+	m = ctx.avail_meta++;
+	m->prev = m->next = 0;
+	return m;
+}
+
+static uint32_t try_avail(struct meta **pm)
+{
+	struct meta *m = *pm;
+	uint32_t first;
+	if (!m) return 0;
+	uint32_t mask = m->avail_mask;
+	if (!mask) {
+		if (!m) return 0;
+		if (!m->freed_mask) {
+			dequeue(pm, m);
+			m = *pm;
+			if (!m) return 0;
+		} else {
+			m = m->next;
+			*pm = m;
+		}
+
+		mask = m->freed_mask;
+
+		// skip fully-free group unless it's the only one
+		// or it's a permanently non-freeable group
+		if (mask == (2u<<m->last_idx)-1 && m->freeable) {
+			m = m->next;
+			*pm = m;
+			mask = m->freed_mask;
+		}
+
+		// activate more slots in a not-fully-active group
+		// if needed, but only as a last resort. prefer using
+		// any other group with free slots. this avoids
+		// touching & dirtying as-yet-unused pages.
+		if (!(mask & ((2u<<m->mem->active_idx)-1))) {
+			if (m->next != m) {
+				m = m->next;
+				*pm = m;
+			} else {
+				int cnt = m->mem->active_idx + 2;
+				int size = size_classes[m->sizeclass]*UNIT;
+				int span = UNIT + size*cnt;
+				// activate up to next 4k boundary
+				while ((span^(span+size-1)) < 4096) {
+					cnt++;
+					span += size;
+				}
+				if (cnt > m->last_idx+1)
+					cnt = m->last_idx+1;
+				m->mem->active_idx = cnt-1;
+			}
+		}
+		mask = activate_group(m);
+		assert(mask);
+		decay_bounces(m->sizeclass);
+	}
+	first = mask&-mask;
+	m->avail_mask = mask-first;
+	return first;
+}
+
+static int alloc_slot(int, size_t);
+
+static struct meta *alloc_group(int sc, size_t req)
+{
+	size_t size = UNIT*size_classes[sc];
+	int i = 0, cnt;
+	unsigned char *p;
+	struct meta *m = alloc_meta();
+	if (!m) return 0;
+	size_t usage = ctx.usage_by_class[sc];
+	size_t pagesize = PGSZ;
+	int active_idx;
+	if (sc < 9) {
+		while (i<2 && 4*small_cnt_tab[sc][i] > usage)
+			i++;
+		cnt = small_cnt_tab[sc][i];
+	} else {
+		// lookup max number of slots fitting in power-of-two size
+		// from a table, along with number of factors of two we
+		// can divide out without a remainder or reaching 1.
+		cnt = med_cnt_tab[sc&3];
+
+		// reduce cnt to avoid excessive eagar allocation.
+		while (!(cnt&1) && 4*cnt > usage)
+			cnt >>= 1;
+
+		// data structures don't support groups whose slot offsets
+		// in units don't fit in 16 bits.
+		while (size*cnt >= 65536*UNIT)
+			cnt >>= 1;
+	}
+
+	// If we selected a count of 1 above but it's not sufficient to use
+	// mmap, increase to 2. Then it might be; if not it will nest.
+	if (cnt==1 && size*cnt+UNIT <= pagesize/2) cnt = 2;
+
+	// All choices of size*cnt are "just below" a power of two, so anything
+	// larger than half the page size should be allocated as whole pages.
+	if (size*cnt+UNIT > pagesize/2) {
+		// check/update bounce counter to start/increase retention
+		// of freed maps, and inhibit use of low-count, odd-size
+		// small mappings and single-slot groups if activated.
+		int nosmall = is_bouncing(sc);
+		account_bounce(sc);
+		step_seq();
+
+		// since the following count reduction opportunities have
+		// an absolute memory usage cost, don't overdo them. count
+		// coarse usage as part of usage.
+		if (!(sc&1) && sc<32) usage += ctx.usage_by_class[sc+1];
+
+		// try to drop to a lower count if the one found above
+		// increases usage by more than 25%. these reduced counts
+		// roughly fill an integral number of pages, just not a
+		// power of two, limiting amount of unusable space.
+		if (4*cnt > usage && !nosmall) {
+			if (0);
+			else if ((sc&3)==1 && size*cnt>8*pagesize) cnt = 2;
+			else if ((sc&3)==2 && size*cnt>4*pagesize) cnt = 3;
+			else if ((sc&3)==0 && size*cnt>8*pagesize) cnt = 3;
+			else if ((sc&3)==0 && size*cnt>2*pagesize) cnt = 5;
+		}
+		size_t needed = size*cnt + UNIT;
+		needed += -needed & (pagesize-1);
+
+		// produce an individually-mmapped allocation if usage is low,
+		// bounce counter hasn't triggered, and either it saves memory
+		// or it avoids eagar slot allocation without wasting too much.
+		if (!nosmall && cnt<=7) {
+			req += IB + UNIT;
+			req += -req & (pagesize-1);
+			if (req<size+UNIT || (req>=4*pagesize && 2*cnt>usage)) {
+				cnt = 1;
+				needed = req;
+			}
+		}
+
+		p = mmap(0, needed, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
+		if (p==MAP_FAILED) {
+			free_meta(m);
+			return 0;
+		}
+		m->maplen = needed>>12;
+		ctx.mmap_counter++;
+		active_idx = (4096-UNIT)/size-1;
+		if (active_idx > cnt-1) active_idx = cnt-1;
+		if (active_idx < 0) active_idx = 0;
+	} else {
+		int j = size_to_class(UNIT+cnt*size-IB);
+		int idx = alloc_slot(j, UNIT+cnt*size-IB);
+		if (idx < 0) {
+			free_meta(m);
+			return 0;
+		}
+		struct meta *g = ctx.active[j];
+		p = enframe(g, idx, UNIT*size_classes[j]-IB, ctx.mmap_counter);
+		m->maplen = 0;
+		p[-3] = (p[-3]&31) | (6<<5);
+		for (int i=0; i<=cnt; i++)
+			p[UNIT+i*size-4] = 0;
+		active_idx = cnt-1;
+	}
+	ctx.usage_by_class[sc] += cnt;
+	m->avail_mask = (2u<<active_idx)-1;
+	m->freed_mask = (2u<<(cnt-1))-1 - m->avail_mask;
+	m->mem = (void *)p;
+	m->mem->meta = m;
+	m->mem->active_idx = active_idx;
+	m->last_idx = cnt-1;
+	m->freeable = 1;
+	m->sizeclass = sc;
+	return m;
+}
+
+static int alloc_slot(int sc, size_t req)
+{
+	uint32_t first = try_avail(&ctx.active[sc]);
+	if (first) return a_ctz_32(first);
+
+	struct meta *g = alloc_group(sc, req);
+	if (!g) return -1;
+
+	g->avail_mask--;
+	queue(&ctx.active[sc], g);
+	return 0;
+}
+
+void *malloc(size_t n)
+{
+	if (size_overflows(n)) return 0;
+	struct meta *g;
+	uint32_t mask, first;
+	int sc;
+	int idx;
+	int ctr;
+
+	if (n >= MMAP_THRESHOLD) {
+		size_t needed = n + IB + UNIT;
+		void *p = mmap(0, needed, PROT_READ|PROT_WRITE,
+			MAP_PRIVATE|MAP_ANON, -1, 0);
+		if (p==MAP_FAILED) return 0;
+		wrlock();
+		step_seq();
+		g = alloc_meta();
+		if (!g) {
+			unlock();
+			munmap(p, needed);
+			return 0;
+		}
+		g->mem = p;
+		g->mem->meta = g;
+		g->last_idx = 0;
+		g->freeable = 1;
+		g->sizeclass = 63;
+		g->maplen = (needed+4095)/4096;
+		g->avail_mask = g->freed_mask = 0;
+		// use a global counter to cycle offset in
+		// individually-mmapped allocations.
+		ctx.mmap_counter++;
+		idx = 0;
+		goto success;
+	}
+
+	sc = size_to_class(n);
+
+	rdlock();
+	g = ctx.active[sc];
+
+	// use coarse size classes initially when there are not yet
+	// any groups of desired size. this allows counts of 2 or 3
+	// to be allocated at first rather than having to start with
+	// 7 or 5, the min counts for even size classes.
+	if (!g && sc>=4 && sc<32 && sc!=6 && !(sc&1) && !ctx.usage_by_class[sc]) {
+		size_t usage = ctx.usage_by_class[sc|1];
+		// if a new group may be allocated, count it toward
+		// usage in deciding if we can use coarse class.
+		if (!ctx.active[sc|1] || (!ctx.active[sc|1]->avail_mask
+		    && !ctx.active[sc|1]->freed_mask))
+			usage += 3;
+		if (usage <= 12)
+			sc |= 1;
+		g = ctx.active[sc];
+	}
+
+	for (;;) {
+		mask = g ? g->avail_mask : 0;
+		first = mask&-mask;
+		if (!first) break;
+		if (RDLOCK_IS_EXCLUSIVE || !MT)
+			g->avail_mask = mask-first;
+		else if (a_cas(&g->avail_mask, mask, mask-first)!=mask)
+			continue;
+		idx = a_ctz_32(first);
+		goto success;
+	}
+	upgradelock();
+
+	idx = alloc_slot(sc, n);
+	if (idx < 0) {
+		unlock();
+		return 0;
+	}
+	g = ctx.active[sc];
+
+success:
+	ctr = ctx.mmap_counter;
+	unlock();
+	return enframe(g, idx, n, ctr);
+}
+
+int is_allzero(void *p)
+{
+	struct meta *g = get_meta(p);
+	return g->sizeclass >= 48 ||
+		get_stride(g) < UNIT*size_classes[g->sizeclass];
+}