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test: handle profiled xallocx no-grow in extent test

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With profiling active, xallocx may decline to grow an allocation that is
not page-aligned.  The profiling path can require sampled xallocx growth
to use page-aligned pointers; otherwise it can return the old usable
size without committing the purged tail.

Observed on Darwin, where decommit/commit are real VM state changes.
The shrink/purge half succeeds and records a decommit, then the
profiling-limited grow skips the matching commit.

This is not Darwin-specific.  Linux no-overcommit should expose the same
mismatch.  Usual Linux overcommit behavior papers it over by making
commit/decommit hooks report unsupported, so both sides of the old
equality check stay false.

Relax the default-path assertion only while profiling is active, and add
a page-aligned case that still requires xallocx shrink and grow to
succeed, preserving commit/merge coverage.

Assisted-by: Codex gpt-5.5 xhigh
This commit is contained in:
Ihar Hrachyshka 2026-07-09 23:34:18 -04:00
parent fb5499aa9c
commit 7029edec97
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1 changed files with 66 additions and 27 deletions
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93
test/integration/extent.c
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@ -4,6 +4,57 @@
#include "jemalloc/internal/arena.h" #include "jemalloc/internal/arena.h"
static void
test_decommit_commit(unsigned arena_ind, int flags, size_t large0,
size_t *purge_mib, size_t purge_miblen, bool expect_xallocx_success) {
void *p;
bool xallocx_success_b, xallocx_success_c;
try_dalloc = false;
try_decommit = true;
p = mallocx(large0 * 2, flags);
expect_ptr_not_null(p, "Unexpected mallocx() error");
did_decommit = false;
did_commit = false;
called_split = false;
did_split = false;
did_merge = false;
xallocx_success_b = (xallocx(p, large0, 0, flags) == large0);
expect_d_eq(mallctlbymib(purge_mib, purge_miblen, NULL, NULL, NULL, 0),
0, "Unexpected arena.%u.purge error", arena_ind);
if (xallocx_success_b) {
expect_true(did_split, "Expected split");
}
xallocx_success_c = (xallocx(p, large0 * 2, 0, flags) == large0 * 2);
if (expect_xallocx_success) {
expect_true(xallocx_success_b, "Expected xallocx shrink");
expect_true(xallocx_success_c, "Expected xallocx grow");
}
if (did_split && xallocx_success_c) {
expect_b_eq(
did_decommit, did_commit, "Expected decommit/commit match");
}
if (xallocx_success_b && xallocx_success_c) {
expect_true(did_merge, "Expected merge");
}
dallocx(p, flags);
try_dalloc = true;
try_decommit = false;
}
static bool
prof_active_enabled(void) {
bool active = false;
size_t sz = sizeof(active);
if (!config_prof) {
return false;
}
expect_d_eq(mallctl("prof.active", &active, &sz, NULL, 0), 0,
"Unexpected prof.active failure");
return active;
}
static void static void
test_extent_body(unsigned arena_ind) { test_extent_body(unsigned arena_ind) {
void *p; void *p;
@ -11,9 +62,13 @@ test_extent_body(unsigned arena_ind) {
size_t purge_mib[3]; size_t purge_mib[3];
size_t purge_miblen; size_t purge_miblen;
int flags; int flags;
bool xallocx_success_a, xallocx_success_b, xallocx_success_c; bool xallocx_success_a;
bool expect_xallocx_success;
bool prof_active;
flags = MALLOCX_ARENA(arena_ind) | MALLOCX_TCACHE_NONE; flags = MALLOCX_ARENA(arena_ind) | MALLOCX_TCACHE_NONE;
expect_xallocx_success = maps_coalesce && try_split && try_merge;
prof_active = prof_active_enabled();
/* Get large size classes. */ /* Get large size classes. */
sz = sizeof(size_t); sz = sizeof(size_t);
@ -58,32 +113,16 @@ test_extent_body(unsigned arena_ind) {
try_dalloc = true; try_dalloc = true;
/* Test decommit/commit and observe split/merge. */ /* Test decommit/commit and observe split/merge. */
try_dalloc = false; test_decommit_commit(arena_ind, flags, large0, purge_mib, purge_miblen,
try_decommit = true; expect_xallocx_success && !prof_active);
p = mallocx(large0 * 2, flags);
expect_ptr_not_null(p, "Unexpected mallocx() error"); /*
did_decommit = false; * Active profiling may decline to grow a non-sampled allocation if it
did_commit = false; * is not page-aligned. Force page alignment to keep deterministic
called_split = false; * coverage for the successful grow/commit/merge path.
did_split = false; */
did_merge = false; test_decommit_commit(arena_ind, flags | MALLOCX_ALIGN(PAGE), large0,
xallocx_success_b = (xallocx(p, large0, 0, flags) == large0); purge_mib, purge_miblen, expect_xallocx_success);
expect_d_eq(mallctlbymib(purge_mib, purge_miblen, NULL, NULL, NULL, 0),
0, "Unexpected arena.%u.purge error", arena_ind);
if (xallocx_success_b) {
expect_true(did_split, "Expected split");
}
xallocx_success_c = (xallocx(p, large0 * 2, 0, flags) == large0 * 2);
if (did_split) {
expect_b_eq(
did_decommit, did_commit, "Expected decommit/commit match");
}
if (xallocx_success_b && xallocx_success_c) {
expect_true(did_merge, "Expected merge");
}
dallocx(p, flags);
try_dalloc = true;
try_decommit = false;
/* Make sure non-large allocation succeeds. */ /* Make sure non-large allocation succeeds. */
p = mallocx(42, flags); p = mallocx(42, flags);