Add memory pool library

Add a memory pool library implemented using C macros. The
obj_pool_gen() macro creates a type-specific memory pool.

The memory pool library is distinguished from the existing specialized
allocators in alloc.c by using a contiguous block for all allocations.
This means that on one hand, long-lived pointers have to be written as
offsets, since the base address changes as the pool grows, but on the
other hand, the entire pool can be easily written to the file system.
This could allow the memory pool to persist between runs of an
application.

For the svn importer, such a facility is useful because each svn
revision can copy trees and files from any previous revision.  The
relevant information for all revisions has to persist somehow to
support incremental runs.

[rr: minor cleanups]
[jn: added tests; removed file system backing for now]

Signed-off-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
David Barr 2010-08-09 17:11:11 -05:00 committed by Junio C Hamano
parent 3f527372d9
commit 4709455db3
5 changed files with 260 additions and 1 deletions

1
.gitignore vendored
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@ -167,6 +167,7 @@
/test-genrandom
/test-index-version
/test-match-trees
/test-obj-pool
/test-parse-options
/test-path-utils
/test-run-command

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@ -409,6 +409,7 @@ TEST_PROGRAMS_NEED_X += test-delta
TEST_PROGRAMS_NEED_X += test-dump-cache-tree
TEST_PROGRAMS_NEED_X += test-genrandom
TEST_PROGRAMS_NEED_X += test-match-trees
TEST_PROGRAMS_NEED_X += test-obj-pool
TEST_PROGRAMS_NEED_X += test-parse-options
TEST_PROGRAMS_NEED_X += test-path-utils
TEST_PROGRAMS_NEED_X += test-run-command
@ -1864,7 +1865,8 @@ xdiff-interface.o $(XDIFF_OBJS): \
xdiff/xinclude.h xdiff/xmacros.h xdiff/xdiff.h xdiff/xtypes.h \
xdiff/xutils.h xdiff/xprepare.h xdiff/xdiffi.h xdiff/xemit.h
$(VCSSVN_OBJS):
$(VCSSVN_OBJS): \
vcs-svn/obj_pool.h
endif
exec_cmd.s exec_cmd.o: EXTRA_CPPFLAGS = \

79
t/t0080-vcs-svn.sh Executable file
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@ -0,0 +1,79 @@
#!/bin/sh
test_description='check infrastructure for svn importer'
. ./test-lib.sh
uint32_max=4294967295
test_expect_success 'obj pool: store data' '
cat <<-\EOF >expected &&
0
1
EOF
test-obj-pool <<-\EOF >actual &&
alloc one 16
set one 13
test one 13
reset one
EOF
test_cmp expected actual
'
test_expect_success 'obj pool: NULL is offset ~0' '
echo "$uint32_max" >expected &&
echo null one | test-obj-pool >actual &&
test_cmp expected actual
'
test_expect_success 'obj pool: out-of-bounds access' '
cat <<-EOF >expected &&
0
0
$uint32_max
$uint32_max
16
20
$uint32_max
EOF
test-obj-pool <<-\EOF >actual &&
alloc one 16
alloc two 16
offset one 20
offset two 20
alloc one 5
offset one 20
free one 1
offset one 20
reset one
reset two
EOF
test_cmp expected actual
'
test_expect_success 'obj pool: high-water mark' '
cat <<-\EOF >expected &&
0
0
10
20
20
20
EOF
test-obj-pool <<-\EOF >actual &&
alloc one 10
committed one
alloc one 10
commit one
committed one
alloc one 10
free one 20
committed one
reset one
EOF
test_cmp expected actual
'
test_done

116
test-obj-pool.c Normal file
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@ -0,0 +1,116 @@
/*
* test-obj-pool.c: code to exercise the svn importer's object pool
*/
#include "cache.h"
#include "vcs-svn/obj_pool.h"
enum pool { POOL_ONE, POOL_TWO };
obj_pool_gen(one, int, 1)
obj_pool_gen(two, int, 4096)
static uint32_t strtouint32(const char *s)
{
char *end;
uintmax_t n = strtoumax(s, &end, 10);
if (*s == '\0' || (*end != '\n' && *end != '\0'))
die("invalid offset: %s", s);
return (uint32_t) n;
}
static void handle_command(const char *command, enum pool pool, const char *arg)
{
switch (*command) {
case 'a':
if (!prefixcmp(command, "alloc ")) {
uint32_t n = strtouint32(arg);
printf("%"PRIu32"\n",
pool == POOL_ONE ?
one_alloc(n) : two_alloc(n));
return;
}
case 'c':
if (!prefixcmp(command, "commit ")) {
pool == POOL_ONE ? one_commit() : two_commit();
return;
}
if (!prefixcmp(command, "committed ")) {
printf("%"PRIu32"\n",
pool == POOL_ONE ?
one_pool.committed : two_pool.committed);
return;
}
case 'f':
if (!prefixcmp(command, "free ")) {
uint32_t n = strtouint32(arg);
pool == POOL_ONE ? one_free(n) : two_free(n);
return;
}
case 'n':
if (!prefixcmp(command, "null ")) {
printf("%"PRIu32"\n",
pool == POOL_ONE ?
one_offset(NULL) : two_offset(NULL));
return;
}
case 'o':
if (!prefixcmp(command, "offset ")) {
uint32_t n = strtouint32(arg);
printf("%"PRIu32"\n",
pool == POOL_ONE ?
one_offset(one_pointer(n)) :
two_offset(two_pointer(n)));
return;
}
case 'r':
if (!prefixcmp(command, "reset ")) {
pool == POOL_ONE ? one_reset() : two_reset();
return;
}
case 's':
if (!prefixcmp(command, "set ")) {
uint32_t n = strtouint32(arg);
if (pool == POOL_ONE)
*one_pointer(n) = 1;
else
*two_pointer(n) = 1;
return;
}
case 't':
if (!prefixcmp(command, "test ")) {
uint32_t n = strtouint32(arg);
printf("%d\n", pool == POOL_ONE ?
*one_pointer(n) : *two_pointer(n));
return;
}
default:
die("unrecognized command: %s", command);
}
}
static void handle_line(const char *line)
{
const char *arg = strchr(line, ' ');
enum pool pool;
if (arg && !prefixcmp(arg + 1, "one"))
pool = POOL_ONE;
else if (arg && !prefixcmp(arg + 1, "two"))
pool = POOL_TWO;
else
die("no pool specified: %s", line);
handle_command(line, pool, arg + strlen("one "));
}
int main(int argc, char *argv[])
{
struct strbuf sb = STRBUF_INIT;
if (argc != 1)
usage("test-obj-str < script");
while (strbuf_getline(&sb, stdin, '\n') != EOF)
handle_line(sb.buf);
strbuf_release(&sb);
return 0;
}

61
vcs-svn/obj_pool.h Normal file
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@ -0,0 +1,61 @@
/*
* Licensed under a two-clause BSD-style license.
* See LICENSE for details.
*/
#ifndef OBJ_POOL_H_
#define OBJ_POOL_H_
#include "git-compat-util.h"
#define MAYBE_UNUSED __attribute__((__unused__))
#define obj_pool_gen(pre, obj_t, initial_capacity) \
static struct { \
uint32_t committed; \
uint32_t size; \
uint32_t capacity; \
obj_t *base; \
} pre##_pool = {0, 0, 0, NULL}; \
static MAYBE_UNUSED uint32_t pre##_alloc(uint32_t count) \
{ \
uint32_t offset; \
if (pre##_pool.size + count > pre##_pool.capacity) { \
while (pre##_pool.size + count > pre##_pool.capacity) \
if (pre##_pool.capacity) \
pre##_pool.capacity *= 2; \
else \
pre##_pool.capacity = initial_capacity; \
pre##_pool.base = realloc(pre##_pool.base, \
pre##_pool.capacity * sizeof(obj_t)); \
} \
offset = pre##_pool.size; \
pre##_pool.size += count; \
return offset; \
} \
static MAYBE_UNUSED void pre##_free(uint32_t count) \
{ \
pre##_pool.size -= count; \
} \
static MAYBE_UNUSED uint32_t pre##_offset(obj_t *obj) \
{ \
return obj == NULL ? ~0 : obj - pre##_pool.base; \
} \
static MAYBE_UNUSED obj_t *pre##_pointer(uint32_t offset) \
{ \
return offset >= pre##_pool.size ? NULL : &pre##_pool.base[offset]; \
} \
static MAYBE_UNUSED void pre##_commit(void) \
{ \
pre##_pool.committed = pre##_pool.size; \
} \
static MAYBE_UNUSED void pre##_reset(void) \
{ \
free(pre##_pool.base); \
pre##_pool.base = NULL; \
pre##_pool.size = 0; \
pre##_pool.capacity = 0; \
pre##_pool.committed = 0; \
}
#endif