From: Attractive Chaos <attractor@live.co.uk>
Date: Wed, 5 Feb 2025 04:14:19 +0000 (-0500)
Subject: Added a faster yet still simple memory pool
X-Git-Url: http://www.kaiwu.me/postgresql/commit/?a=commitdiff_plain;h=5c1451caa1ee476624d00eed71810532c89b82d1;p=klib.git

Added a faster yet still simple memory pool
---

diff --git a/kmempool.c b/kmempool.c
new file mode 100644
index 0000000..8154112
--- /dev/null
+++ b/kmempool.c
@@ -0,0 +1,73 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include "kmempool.h"
+
+#define Malloc(type, cnt)       ((type*)malloc((cnt) * sizeof(type)))
+#define Calloc(type, cnt)       ((type*)calloc((cnt), sizeof(type)))
+#define Realloc(type, ptr, cnt) ((type*)realloc((ptr), (cnt) * sizeof(type)))
+
+typedef struct {
+	uint32_t sz; // size of an entry
+	uint32_t chunk_size; // number of entries in a chunk
+	uint32_t n_chunk; // number of chunks
+	uint8_t *p; // pointing to an entry that can be allocated from a chunk
+	uint8_t *p_end; // end of the current chunk
+	uint8_t **chunk; // list of chunks
+	uint32_t n_buf, m_buf; // number/max number of buffered free entries
+	void **buf; // list of pointers to free entries
+} kmempool_t;
+
+static void kmp_add_chunk(kmempool_t *mp) // add a new chunk
+{
+	uint64_t x = (uint64_t)mp->sz * mp->chunk_size;
+	mp->chunk = Realloc(uint8_t*, mp->chunk, mp->n_chunk + 1);
+	mp->p = mp->chunk[mp->n_chunk++] = Calloc(uint8_t, x);
+	mp->p_end = mp->p + x;
+}
+
+void *kmp_init2(unsigned sz, unsigned chunk_size)
+{
+	kmempool_t *mp;
+	mp = Calloc(kmempool_t, 1);
+	mp->sz = sz, mp->chunk_size = chunk_size;
+	kmp_add_chunk(mp);
+	return mp;
+}
+
+void *kmp_init(unsigned sz) // fixed chunk size
+{
+	return kmp_init2(sz, 0x10000);
+}
+
+void kmp_destroy(void *mp_)
+{
+	kmempool_t *mp = (kmempool_t*)mp_;
+	uint32_t i;
+	for (i = 0; i < mp->n_chunk; ++i) // free all chunks
+		free(mp->chunk[i]);
+	free(mp->chunk); free(mp->buf); free(mp);
+}
+
+void *kmp_alloc(void *mp_)
+{
+	kmempool_t *mp = (kmempool_t*)mp_;
+	void *ret;
+	if (mp->n_buf > 0) { // there are buffered free entries
+		ret = mp->buf[--mp->n_buf];
+	} else { // need to "allocate" from chunks
+		if (mp->p == mp->p_end) kmp_add_chunk(mp); // chunk full; add a new one
+		ret = (void*)mp->p;
+		mp->p += mp->sz;
+	}
+	return ret;
+}
+
+void kmp_free(void *mp_, void *p)
+{
+	kmempool_t *mp = (kmempool_t*)mp_;
+	if (mp->n_buf == mp->m_buf) { // then enlarge the buffer
+		mp->m_buf += (mp->m_buf>>1) + 16;
+		mp->buf = Realloc(void*, mp->buf, mp->m_buf);
+	}
+	mp->buf[mp->n_buf++] = p;
+}
diff --git a/kmempool.h b/kmempool.h
new file mode 100644
index 0000000..fcbda8e
--- /dev/null
+++ b/kmempool.h
@@ -0,0 +1,17 @@
+#ifndef AC_KMEMPOOL_H
+#define AC_KMEMPOOL_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void *kmp_init(unsigned sz);
+void kmp_destroy(void *mp);
+void *kmp_alloc(void *mp);
+void kmp_free(void *mp, void *p);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif