Re: [RFC] O(1) proc_pid_readdir

[William Lee Irwin III <wli@holomorphy.com>]

Ingo Molnar wrote:
>> have you seen my "procfs/procps threading performance speedup" patch? It
>> does something like this.

On Sun, Mar 16, 2003 at 10:24:34PM +0100, Manfred Spraul wrote:
> Interesting patch. Do seekdir and telldir still work? I think you must 
> detect lseek calls and invalidate the cookie - either by hooking lseek 
> or by looking at f_version.
> I think my solution for proc_pid_readdir() is better: You must fall back 
> to the old algorithm if the pid number stored in f_private got invalid 
> between two syscalls. I've modified the hash table slightly and search 
> for the next pid value directly, which works even if the current 
> position disappeared.

I'm heavily on the side of deterministic bounds here (these things trip
the NMI oopser, so if the bounds aren't deterministic, neither is
stability), so I favor manfred's proc_pid_readdir() algorithm.

It actually looks compatible with your prior patch aside from replacing
and/or modifying its get_pid_list() speedup.


-- wli