Messages in this thread | | | Subject | Re: [PATCH] get_pid() performance fix | From | OGAWA Hirofumi <> | Date | Sat, 16 Mar 2002 00:16:48 +0900 |
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Whoops! I'm sorry. previous email was the middle of writing.
Hubertus Franke <frankeh@watson.ibm.com> writes:
> + if (i == PID_MAP_SIZE) { > + if (again) { > + /* we didn't find any pid , sweep and try again */ > + again = 0; > + memset(pid_map, 0, PID_MAP_SIZE * sizeof(unsigned long)); > + last_pid = RESERVED_PIDS; > + goto repeat; > + } > + next_safe = RESERVED_PIDS; > + return 0;
Probably, the bug is here.
the following is test case: ./getpid1 -r300 -c3
case 3: populate_all(0, 1); pid = get_pid(0); printf("new pid: %d\n", pid); tsk = find_task_by_pid(400); del_task(tsk); pid = get_pid(0); printf("new pid: %d\n", pid);
break;
result, new pid: 0 new pid: 1
> + } > + > + fpos = ffz(mask); > + i &= (PID_MAX-1); > + last_pid = (i << SHIFT_PER_LONG) + fpos; > + > + /* find next save pid */ > + mask &= ~((1 << fpos) - 1); > + > + while ((mask == 0) && (++i < PID_MAP_SIZE)) > + mask = pid_map[i]; > + > + if (i==PID_MAP_SIZE) > + next_safe = PID_MAX; > + else > + next_safe = (i << SHIFT_PER_LONG) + ffs(mask) - 1; > + return last_pid; > +} > + > static int get_pid(unsigned long flags) > { > - static int next_safe = PID_MAX; > struct task_struct *p; > - int pid; > + int pid,beginpid; > > if (flags & CLONE_PID) > return current->pid; > > spin_lock(&lastpid_lock); > + beginpid = last_pid; > if((++last_pid) & 0xffff8000) { > - last_pid = 300; /* Skip daemons etc. */ > + last_pid = RESERVED_PIDS; /* Skip daemons etc. */ > goto inside; > } > if(last_pid >= next_safe) { > inside: > next_safe = PID_MAX; > read_lock(&tasklist_lock); > + if (nr_threads > GETPID_THRESHOLD) { > + last_pid = get_pid_by_map(last_pid); > + } else { > repeat: > for_each_task(p) { > if(p->pid == last_pid || > @@ -151,9 +228,11 @@ > p->session == last_pid) { > if(++last_pid >= next_safe) { > if(last_pid & 0xffff8000) > - last_pid = 300; > + last_pid = RESERVED_PIDS; > next_safe = PID_MAX; > } > + if(unlikely(last_pid == beginpid)) > + goto nomorepids; > goto repeat; > } > if(p->pid > last_pid && next_safe > p->pid) > @@ -162,6 +241,9 @@ > next_safe = p->pgrp; > if(p->session > last_pid && next_safe > p->session) > next_safe = p->session; > + if(p->tgid > last_pid && next_safe > p->tgid) > + next_safe = p->tgid; > + } > } > read_unlock(&tasklist_lock); > } > @@ -169,6 +251,10 @@ > spin_unlock(&lastpid_lock); > > return pid; > +nomorepids:
Probably, the following line are required, here.
+ next_safe = RESERVED_PIDS; /* or 0 */
> + read_unlock(&tasklist_lock); > + spin_unlock(&lastpid_lock); > + return 0; > }
Basically nice, I think.
BTW, How about using the __set_bit(), find_next_zero_bit(), and find_next_bit() in get_pid_by_map().
Thanks for nice work. -- OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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