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Add a per-thread struct task cache. 

This allows us to save some malloc()/free() calls.

The structs can leak on program exit, but an external vector to store
them could fix this.

As it stands, this isn't really useful: in multiple tests with the linux
kernel tree, the p_old branch was taken between 0 and 3 times in a full
run.
This commit is contained in:
Érico Nogueira 2022-06-12 21:33:57 -03:00
parent 630ccbf1ce
commit a626ae594d
1 changed files with 10 additions and 3 deletions
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13
remove.c
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@ -128,7 +128,8 @@ static inline void recurse_into_parents(struct task *t)
static void *process_queue_item(void *arg)
{
struct queue *q = arg;
struct task t;
/* p_old is a struct task cache; this means each thread can leak one struct task in total */
struct task t, *p_old = NULL;
while (1) {
queue_remove(q, &t);
@ -173,7 +174,13 @@ fast_path_dir:
/* lazy allocation of p and other operations */
if (!p) {
p = malloc(sizeof *p);
if (p_old) {
p = p_old;
p_old = NULL;
puts("used p_old");
} else {
p = malloc(sizeof *p);
}
*p = t;
/* access happens only after mutex lock and release */
atomic_store_explicit(&p->removed_count, ACQUIRED, memory_order_relaxed);
@ -200,8 +207,8 @@ fast_path_dir:
p->files = n-1; /* other thread will compare against removed_count-1 */
unsigned rc = atomic_fetch_and_explicit(&p->removed_count, ~ACQUIRED, memory_order_release);
if (rc == (n|ACQUIRED)) {
free(p);
/* this branch is taken when other threads have already removed all of p's children */
p_old = p;
if (rmdir(t.path)) {
fprintf(stderr, "atomic rmdir failed '%s': %m\n", t.path);
} else {