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[process_madvise] Make init lazy so that python tests pass. Reset the pidfd on fork

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This commit is contained in:
Slobodan Predolac 2025-07-25 10:14:28 -07:00 • committed by guangli-dai
parent 07a3742f72
commit dc2c0276e8
4 changed files with 34 additions and 7 deletions
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2
include/jemalloc/internal/atomic.h
View file

@ -89,6 +89,8 @@ JEMALLOC_GENERATE_ATOMICS(bool, b, 0)
JEMALLOC_GENERATE_EXPANDED_INT_ATOMICS(unsigned, u, LG_SIZEOF_INT)
JEMALLOC_GENERATE_EXPANDED_INT_ATOMICS(int, i, LG_SIZEOF_INT)
JEMALLOC_GENERATE_EXPANDED_INT_ATOMICS(size_t, zu, LG_SIZEOF_PTR)
JEMALLOC_GENERATE_EXPANDED_INT_ATOMICS(ssize_t, zd, LG_SIZEOF_PTR)

1
include/jemalloc/internal/pages.h
View file

@ -127,5 +127,6 @@ bool pages_boot(void);
void pages_set_thp_state(void *ptr, size_t size);
void pages_mark_guards(void *head, void *tail);
void pages_unmark_guards(void *head, void *tail);
void pages_postfork_child(void);
#endif /* JEMALLOC_INTERNAL_PAGES_EXTERNS_H */

1
src/jemalloc.c
View file

@ -4549,6 +4549,7 @@ jemalloc_postfork_child(void) {
malloc_mutex_postfork_child(tsd_tsdn(tsd), &arenas_lock);
tcache_postfork_child(tsd_tsdn(tsd));
ctl_postfork_child(tsd_tsdn(tsd));
pages_postfork_child();
}
/******************************************************************************/

37
src/pages.c
View file

@ -621,7 +621,7 @@ pages_dodump(void *addr, size_t size) {
#ifdef JEMALLOC_HAVE_PROCESS_MADVISE
# include <sys/mman.h>
# include <sys/syscall.h>
static int pidfd;
static atomic_i_t process_madvise_pidfd = ATOMIC_INIT(-1);
static bool
init_process_madvise(void) {
@ -632,11 +632,6 @@ init_process_madvise(void) {
if (opt_process_madvise_max_batch > PROCESS_MADVISE_MAX_BATCH_LIMIT) {
opt_process_madvise_max_batch = PROCESS_MADVISE_MAX_BATCH_LIMIT;
}
pid_t pid = getpid();
pidfd = syscall(SYS_pidfd_open, pid, 0);
if (pidfd == -1) {
return true;
}
return false;
}
@ -651,12 +646,38 @@ init_process_madvise(void) {
static bool
pages_purge_process_madvise_impl(
void *vec, size_t vec_len, size_t total_bytes) {
size_t purged_bytes = (size_t)syscall(JE_SYS_PROCESS_MADVISE_NR, pidfd,
int pid_fd = atomic_load_i(&process_madvise_pidfd, ATOMIC_SEQ_CST);
while (pid_fd == -1) {
int newfd = syscall(SYS_pidfd_open, getpid(), 0);
if (newfd == -1) {
return true;
}
if (!atomic_compare_exchange_strong_i(&process_madvise_pidfd,
&pid_fd, newfd,
ATOMIC_SEQ_CST,
ATOMIC_SEQ_CST)) {
/* Someone else set the fd, so we close ours */
assert(pid_fd != -1);
close(newfd);
} else {
pid_fd = newfd;
}
}
size_t purged_bytes = (size_t)syscall(JE_SYS_PROCESS_MADVISE_NR, pid_fd,
(struct iovec *)vec, vec_len, MADV_DONTNEED, 0);
return purged_bytes != total_bytes;
}
void pages_postfork_child(void) {
/* Reset the file descriptor we inherited from parent process */
int pid_fd = atomic_load_i(&process_madvise_pidfd, ATOMIC_SEQ_CST);
if (pid_fd != -1) {
atomic_store_i(&process_madvise_pidfd, -1, ATOMIC_SEQ_CST);
close(pid_fd);
}
}
#else
static bool
@ -671,6 +692,8 @@ pages_purge_process_madvise_impl(
return true;
}
void pages_postfork_child(void) {}
#endif
bool