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Add a static pre-allocated buffer to isc_buffer_t

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When the buffer is allocated via isc_buffer_allocate() and the size is
smaller or equal ISC_BUFFER_STATIC_SIZE (currently 512 bytes), the
buffer will be allocated as a flexible array member in the buffer
structure itself instead of allocating it on the heap.  This should help
when the buffer is used on the hot-path with small allocations.
This commit is contained in:
Ondřej Surý
2022-12-15 22:51:52 +01:00
parent 6bd2b34180
commit 2ddea1e41c
3 changed files with 69 additions and 61 deletions
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64
lib/isc/buffer.c
View File

@@ -120,72 +120,80 @@ isc_buffer_copyregion(isc_buffer_t *b, const isc_region_t *r) {
}
void
isc_buffer_allocate(isc_mem_t *mctx, isc_buffer_t **dynbuffer,
isc_buffer_allocate(isc_mem_t *mctx, isc_buffer_t **dbufp,
unsigned int length) {
REQUIRE(dynbuffer != NULL && *dynbuffer == NULL);
REQUIRE(dbufp != NULL && *dbufp == NULL);
isc_buffer_t *dbuf = isc_mem_get(mctx, sizeof(isc_buffer_t));
unsigned char *bdata = isc_mem_get(mctx, length);
isc_buffer_t *dbuf = isc_mem_get(mctx, sizeof(*dbuf) + length);
uint8_t *bdata = (uint8_t *)dbuf + sizeof(*dbuf);
isc_buffer_init(dbuf, bdata, length);
dbuf->extra = length;
dbuf->mctx = mctx;
*dynbuffer = dbuf;
*dbufp = dbuf;
}
isc_result_t
isc_buffer_reserve(isc_buffer_t *dynbuffer, unsigned int size) {
isc_buffer_reserve(isc_buffer_t *dbuf, unsigned int size) {
REQUIRE(ISC_BUFFER_VALID(dbuf));
size_t len;
uint8_t *bdata = (uint8_t *)dbuf + sizeof(*dbuf);
REQUIRE(ISC_BUFFER_VALID(dynbuffer));
len = dynbuffer->length;
if ((len - dynbuffer->used) >= size) {
len = dbuf->length;
if ((len - dbuf->used) >= size) {
return (ISC_R_SUCCESS);
}
if (dynbuffer->mctx == NULL) {
if (dbuf->mctx == NULL) {
return (ISC_R_NOSPACE);
}
/* Round to nearest buffer size increment */
len = size + dynbuffer->used;
len = (len + ISC_BUFFER_INCR - 1 - ((len - 1) % ISC_BUFFER_INCR));
len = size + dbuf->used;
len = ISC_ALIGN(len, ISC_BUFFER_INCR);
/* Cap at UINT_MAX */
if (len > UINT_MAX) {
len = UINT_MAX;
}
if ((len - dynbuffer->used) < size) {
if ((len - dbuf->used) < size) {
return (ISC_R_NOMEMORY);
}
dynbuffer->base = isc_mem_reget(dynbuffer->mctx, dynbuffer->base,
dynbuffer->length, len);
dynbuffer->length = (unsigned int)len;
if (dbuf->base == bdata) {
dbuf->base = isc_mem_get(dbuf->mctx, len);
memmove(dbuf->base, bdata, dbuf->used);
} else {
dbuf->base = isc_mem_reget(dbuf->mctx, dbuf->base, dbuf->length,
len);
}
dbuf->length = (unsigned int)len;
return (ISC_R_SUCCESS);
}
void
isc_buffer_free(isc_buffer_t **dynbuffer) {
isc_buffer_t *dbuf;
isc_mem_t *mctx;
isc_buffer_free(isc_buffer_t **dbufp) {
REQUIRE(dbufp != NULL && ISC_BUFFER_VALID(*dbufp));
REQUIRE((*dbufp)->mctx != NULL);
REQUIRE(dynbuffer != NULL);
REQUIRE(ISC_BUFFER_VALID(*dynbuffer));
REQUIRE((*dynbuffer)->mctx != NULL);
isc_buffer_t *dbuf = *dbufp;
isc_mem_t *mctx = dbuf->mctx;
uint8_t *bdata = (uint8_t *)dbuf + sizeof(*dbuf);
unsigned int extra = dbuf->extra;
dbuf = *dynbuffer;
*dynbuffer = NULL; /* destroy external reference */
mctx = dbuf->mctx;
*dbufp = NULL; /* destroy external reference */
dbuf->mctx = NULL;
if (dbuf->base != bdata) {
isc_mem_put(mctx, dbuf->base, dbuf->length);
}
isc_buffer_invalidate(dbuf);
isc_mem_put(mctx, dbuf, sizeof(isc_buffer_t));
isc_mem_put(mctx, dbuf, sizeof(*dbuf) + extra);
}
isc_result_t

29
lib/isc/include/isc/buffer.h
View File

@@ -128,7 +128,7 @@ ISC_LANG_BEGINDECLS
* space in a buffer, we round the allocated buffer length up to the
* nearest * multiple of this value.
*/
#define ISC_BUFFER_INCR 2048
#define ISC_BUFFER_INCR 512
/*
* The following macros MUST be used only on valid buffers. It is the
@@ -177,6 +177,8 @@ struct isc_buffer {
unsigned int used;
unsigned int current;
unsigned int active;
/*! The extra bytes allocated for dynamic buffer */
unsigned int extra;
/*@}*/
/*! linkable */
ISC_LINK(isc_buffer_t) link;
@@ -184,6 +186,8 @@ struct isc_buffer {
isc_mem_t *mctx;
};
#define ISC_BUFFER_STATIC_SIZE 512
/***
*** Functions
***/
@@ -509,10 +513,12 @@ static inline void
isc_buffer_init(isc_buffer_t *b, void *base, unsigned int length) {
ISC_REQUIRE(b != NULL);
*b = (isc_buffer_t){ .base = base,
*b = (isc_buffer_t){
.base = base,
.length = length,
.magic = ISC_BUFFER_MAGIC };
ISC_LINK_INIT(b, link);
.link = ISC_LINK_INITIALIZER,
.magic = ISC_BUFFER_MAGIC,
};
}
/*!
@@ -521,8 +527,10 @@ isc_buffer_init(isc_buffer_t *b, void *base, unsigned int length) {
*/
static inline void
isc_buffer_initnull(isc_buffer_t *b) {
*b = (isc_buffer_t){ .magic = ISC_BUFFER_MAGIC };
ISC_LINK_INIT(b, link);
*b = (isc_buffer_t){
.link = ISC_LINK_INITIALIZER,
.magic = ISC_BUFFER_MAGIC,
};
}
/*!
@@ -560,12 +568,9 @@ isc_buffer_invalidate(isc_buffer_t *b) {
ISC_REQUIRE(!ISC_LINK_LINKED(b, link));
ISC_REQUIRE(b->mctx == NULL);
b->magic = 0;
b->base = NULL;
b->length = 0;
b->used = 0;
b->current = 0;
b->active = 0;
*b = (isc_buffer_t){
.magic = 0,
};
}
/*!

33
tests/isc/buffer_test.c
View File

@@ -42,48 +42,44 @@ ISC_RUN_TEST_IMPL(isc_buffer_reserve) {
UNUSED(state);
b = NULL;
isc_buffer_allocate(mctx, &b, 1024);
assert_int_equal(b->length, 1024);
isc_buffer_allocate(mctx, &b, ISC_BUFFER_INCR);
assert_int_equal(b->length, ISC_BUFFER_INCR);
/*
* 1024 bytes should already be available, so this call does
* 512 bytes should already be available, so this call does
* nothing.
*/
result = isc_buffer_reserve(b, 1024);
result = isc_buffer_reserve(b, 512);
assert_int_equal(result, ISC_R_SUCCESS);
assert_true(ISC_BUFFER_VALID(b));
assert_non_null(b);
assert_int_equal(b->length, 1024);
assert_int_equal(b->length, ISC_BUFFER_INCR);
/*
* This call should grow it to 2048 bytes as only 1024 bytes are
* This call should grow it to 1536 bytes as only 1024 bytes are
* available in the buffer.
*/
result = isc_buffer_reserve(b, 1025);
assert_int_equal(result, ISC_R_SUCCESS);
assert_true(ISC_BUFFER_VALID(b));
assert_non_null(b);
assert_int_equal(b->length, 2048);
assert_int_equal(b->length, 3 * ISC_BUFFER_INCR);
/*
* 2048 bytes should already be available, so this call does
* 1536 bytes should already be available, so this call does
* nothing.
*/
result = isc_buffer_reserve(b, 2000);
result = isc_buffer_reserve(b, 1500);
assert_int_equal(result, ISC_R_SUCCESS);
assert_true(ISC_BUFFER_VALID(b));
assert_non_null(b);
assert_int_equal(b->length, 2048);
assert_int_equal(b->length, 3 * ISC_BUFFER_INCR);
/*
* This call should grow it to 4096 bytes as only 2048 bytes are
* This call should grow it to 4096 bytes as only 1536 bytes are
* available in the buffer.
*/
result = isc_buffer_reserve(b, 3000);
result = isc_buffer_reserve(b, 3585);
assert_int_equal(result, ISC_R_SUCCESS);
assert_true(ISC_BUFFER_VALID(b));
assert_non_null(b);
assert_int_equal(b->length, 4096);
assert_int_equal(b->length, 8 * ISC_BUFFER_INCR);
/* Consume some of the buffer so we can run the next test. */
isc_buffer_add(b, 4096);
@@ -93,9 +89,8 @@ ISC_RUN_TEST_IMPL(isc_buffer_reserve) {
*/
result = isc_buffer_reserve(b, UINT_MAX);
assert_int_equal(result, ISC_R_NOMEMORY);
assert_true(ISC_BUFFER_VALID(b));
assert_non_null(b);
assert_int_equal(b->length, 4096);
assert_int_equal(b->length, 8 * ISC_BUFFER_INCR);
isc_buffer_free(&b);
}