* Sun, 2 Sep 2007 20:36:19 +0200
>
I see, that in many places all pre-checks are done in negative form
with resulting return or jump out. In this case, if function was called,
what likely() path is?
> +static void resize_pid_hash(void)
> +{
> + unsigned int old_shift, new_shift;
> +
> + if (system_state != SYSTEM_RUNNING)
> + return;
> +
> + old_shift = cur_pid_hash->shift;
> + new_shift = ilog2(nr_pids * 2 - 1);
> + if (new_shift == old_shift)
> + return;
> +
> + if (!mutex_trylock(&dyn_pidhash.resize_mutex))
> + return;
that one or this?
==
if (system_state == SYSTEM_RUNNING) {
old_shift = cur_pid_hash->shift;
new_shift = ilog2(nr_pids * 2 - 1);
if (new_shift != old_shift &&
mutex_trylock(&dyn_pidhash.resize_mutex)) {
==
> + old_shift = cur_pid_hash->shift;
> + new_shift = ilog2(nr_pids * 2 - 1);
/* hope this repetition is needed by design */
...
> + mutex_unlock(&dyn_pidhash.resize_mutex);
}
What is more efficient in general sense,
as opposed to s,3,2,1,0 Optimized?
> + if (new_shift != old_shift) {
> + struct pid_hash *ph, *ret;
> + unsigned int idx = ph_cur_idx ^ 1;
> + ph = &pid_hashes[idx];
> + if (!init_pid_hash(ph, new_shift)) {
> + ph_cur_idx = idx;
> +
> + ret = dyn_data_replace(&dyn_pidhash, dd_transfer_pids,
> ph);
> + BUG_ON(ret == ph);
> + BUG_ON(ret != &pid_hashes[idx ^ 1]);
> + /* XXX: kfree(ret->table) */
> + ret->shift = -1;
> + ret->table = NULL;
> + }
> + }
> + mutex_unlock(&dyn_pidhash.resize_mutex);
> +}
> +
Thanks.
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