Messages in this thread | | | Subject | Re: [PATCH] get_pid() performance fix | From | OGAWA Hirofumi <> | Date | Sat, 16 Mar 2002 14:12:16 +0900 |
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Hubertus Franke <frankeh@watson.ibm.com> writes:
> On Friday 15 March 2002 10:16 am, OGAWA Hirofumi wrote: > > 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. No bug .... > > > > > + 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, honestly I only tried testcase 2. > But looking at your suggestion its not clear to me whether > there is a bug. > Remember we need to determine a valid interval [ last_pid .. next_safe ). > In the pid_map function, if no pid is available, then > [ PID_MAX .. PID_MAX ) will be returned. > The other path should also end up with this as well. > Could you point where you see this not happening.
Maybe my point was unclear. Sorry.
Please consider what happens after using up pid. Then, get_pid_by_map() returns 0.
And last_pid = 0, next_safe = RESERVED_PIDS. After it, get_pid() returns the values between 0 and RESERVED_PIDS.
And the line which I added is also the same reason.
Regards. -- 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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