linux-kernel - Re: [RFC] ps command race fix

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Message-Id: <20060725121640.246a3720.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 25 Jul 2006 12:16:40 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	akpm@...l.org, pj@....com, linux-kernel@...r.kernel.org,
	ebiederm@...ssion.com
Subject: Re: [RFC] ps command race fix

On Tue, 25 Jul 2006 11:50:04 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> BTW, how large pids and how many proccess in a (heavy and big) system ?
> 
I found
/*
 * A maximum of 4 million PIDs should be enough for a while.
 * [NOTE: PID/TIDs are limited to 2^29 ~= 500+ million, see futex.h.]
 */
#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
        (sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT))

...we have to manage 4 millions tids.

I'll try to make use of pidmap array which is already maintained in pid.c
and to avoid using extra memory.

Thanks,
-Kame

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