From e59054270c6e37fd08fdd5d0231edd17c7f7495a Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Tue, 30 Apr 2019 10:13:57 +0200 Subject: alloc-util: reintroduce malloc_usable_size() into greedy_realloc() This is another attempt at d4b604baeadbb2498e4f2c3e260260eed210f5d6 and #12438 Instead of blindly using the extra allocated space, let's do so only after telling libc about it, via a second realloc(). The second realloc() should be quick, since it never has to copy memory around. --- src/basic/alloc-util.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/src/basic/alloc-util.c b/src/basic/alloc-util.c index f4bd33f4e0..a16db6824f 100644 --- a/src/basic/alloc-util.c +++ b/src/basic/alloc-util.c @@ -1,5 +1,6 @@ /* SPDX-License-Identifier: LGPL-2.1+ */ +#include #include #include @@ -63,6 +64,29 @@ void* greedy_realloc(void **p, size_t *allocated, size_t need, size_t size) { if (!q) return NULL; + if (size > 0) { + size_t bn; + + /* Adjust for the 64 byte minimum */ + newalloc = a / size; + + bn = malloc_usable_size(q) / size; + if (bn > newalloc) { + void *qq; + + /* The actual size allocated is larger than what we asked for. Let's call realloc() again to + * take possession of the extra space. This should be cheap, since libc doesn't have to move + * the memory for this. */ + + qq = realloc(q, bn * size); + if (_likely_(qq)) { + *p = qq; + *allocated = bn; + return qq; + } + } + } + *p = q; *allocated = newalloc; return q; -- cgit v1.2.1 From 413644757628952af3c9c503be579f094517093d Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Tue, 30 Apr 2019 10:17:19 +0200 Subject: test-alloc-util: let's test a few more things around GREEDY_REALLOC() --- src/test/test-alloc-util.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) diff --git a/src/test/test-alloc-util.c b/src/test/test-alloc-util.c index ad10eb178a..2dfdfe35ec 100644 --- a/src/test/test-alloc-util.c +++ b/src/test/test-alloc-util.c @@ -1,5 +1,6 @@ /* SPDX-License-Identifier: LGPL-2.1+ */ +#include #include #include "alloc-util.h" @@ -21,21 +22,35 @@ static void test_alloca(void) { static void test_GREEDY_REALLOC(void) { _cleanup_free_ int *a = NULL, *b = NULL; - size_t n_allocated = 0, i; + size_t n_allocated = 0, i, j; - /* Give valgrind a chance to verify our realloc operations */ + /* Give valgrind a chance to verify our realloc() operations */ - for (i = 0; i < 2048; i++) { + for (i = 0; i < 20480; i++) { assert_se(GREEDY_REALLOC(a, n_allocated, i + 1)); - a[i] = i; + assert_se(n_allocated >= i + 1); + assert_se(malloc_usable_size(a) >= (i + 1) * sizeof(int)); + a[i] = (int) i; assert_se(GREEDY_REALLOC(a, n_allocated, i / 2)); + assert_se(n_allocated >= i / 2); + assert_se(malloc_usable_size(a) >= (i / 2) * sizeof(int)); } - for (i = 30, n_allocated = 0; i < 2048; i+=7) { + for (j = 0; j < i / 2; j++) + assert_se(a[j] == (int) j); + + for (i = 30, n_allocated = 0; i < 20480; i += 7) { assert_se(GREEDY_REALLOC(b, n_allocated, i + 1)); - b[i] = i; + assert_se(n_allocated >= i + 1); + assert_se(malloc_usable_size(b) >= (i + 1) * sizeof(int)); + b[i] = (int) i; assert_se(GREEDY_REALLOC(b, n_allocated, i / 2)); + assert_se(n_allocated >= i / 2); + assert_se(malloc_usable_size(b) >= (i / 2) * sizeof(int)); } + + for (j = 30; j < i / 2; j += 7) + assert_se(b[j] == (int) j); } static void test_memdup_multiply_and_greedy_realloc(void) { -- cgit v1.2.1