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From: ebiederm@xmission.com (Eric W. Biederman)
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Hubertus Franke <frankeh@watson.ibm.com>,
	Dave Hansen <haveblue@us.ibm.com>, Greg KH <greg@kroah.com>,
	"Serge E. Hallyn" <serue@us.ibm.com>,
	Arjan van de Ven <arjan@infradead.org>,
	linux-kernel@vger.kernel.org, Cedric Le Goater <clg@fr.ibm.com>
Subject: Re: RFC [patch 13/34] PID Virtualization Define new task_pid api
Date: Tue, 24 Jan 2006 12:26:20 -0700	[thread overview]
Message-ID: <m17j8pl95v.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <1138062125.24808.47.camel@localhost.localdomain> (Alan Cox's message of "Tue, 24 Jan 2006 00:22:05 +0000")

Alan Cox <alan@lxorguk.ukuu.org.uk> writes:

> On Llu, 2006-01-23 at 14:30 -0700, Eric W. Biederman wrote:
>> The short observation is currently we use at most 22bits of the pid
>> space, and we don't need a huge number of containers so combining them
>> into one integer makes sense for an efficient implementation, and it
>> is cheaper than comparing pointers.
>
> Currently. In addition it becomes more costly the moment you have to
> start masking them. Remember the point of this was to virtualise the
> pid, so you are going to add a ton of masking versus a cheap extra
> comparison from the same cache line. And you lose pid space you may well
> need in the future for the sake of a quick hack.

I do disagree that as I am envisioning it will get in the way but I
do agree that putting them in the unsigned long may be overkill.

There is at least NFS lockd that appreciates having a single integer
per process unique identifier.  So there is a practical basis for
wanting such a thing.

At least for this first round I think talking about a kpid
as a container, pid pair makes a lot of sense for the moment, as
the other implementations just confuse things.

>> And there will be at least one processes id assigned to the pid space
>> from the outside pid space unless we choose to break waitpid, and friends.
>
> That comes out in the wash because it is already done by process tree
> pointers anyway. It has to be because using ->ppid would be racy.

Possibly.  Again, it is one of the more interesting cases, to get
just right.

However it looks to me that the biggest challenge right now about
development is the size of a patch to change any one of these things.
So it looks to me like the first step is to add wrappers for common idioms
that use pids, like printing the name of a task or testing if it is the
init task or if it is an idle task.

Or can you think of a case where it would be wise to leave
both the type and size of current->pid alone?

Eric

  reply	other threads:[~2006-01-24 19:28 UTC|newest]

Thread overview: 136+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-01-17 14:32 RFC [patch 00/34] PID Virtualization Overview Serge Hallyn
2006-01-17 14:32 ` RFC [patch 01/34] PID Virtualization Change pid accesses: drivers Serge Hallyn
2006-01-17 14:33 ` RFC [patch 02/34] PID Virtualization Change pid accesses: most archs Serge Hallyn
2006-01-17 14:33 ` RFC [patch 03/34] PID Virtualization Change pid accesses: filesystems Serge Hallyn
2006-01-17 14:33 ` RFC [patch 04/34] PID Virtualization Change pid accesses: include/ Serge Hallyn
2006-01-17 14:33 ` RFC [patch 05/34] PID Virtualization Change pid accesses: ipc Serge Hallyn
2006-01-17 14:33 ` RFC [patch 06/34] PID Virtualization Change pid accesses: kernel/ Serge Hallyn
2006-01-17 14:33 ` RFC [patch 07/34] PID Virtualization Change pid accesses: lib/ Serge Hallyn
2006-01-17 14:33 ` RFC [patch 08/34] PID Virtualization Change pid accesses: mm/ Serge Hallyn
2006-01-17 14:33 ` RFC [patch 09/34] PID Virtualization Change pid accesses: net/ Serge Hallyn
2006-01-17 14:33 ` RFC [patch 10/34] PID Virtualization Change pid accesses: security/ Serge Hallyn
2006-01-17 14:33 ` RFC [patch 11/34] PID Virtualization Change pid accesses: sound/ Serge Hallyn
2006-01-17 14:33 ` RFC [patch 12/34] PID Virtualization Change pid accesses: ia64 and mips Serge Hallyn
2006-01-17 14:33 ` RFC [patch 13/34] PID Virtualization Define new task_pid api Serge Hallyn
2006-01-17 15:32   ` Arjan van de Ven
2006-01-17 15:56     ` Serge E. Hallyn
2006-01-17 16:02       ` Arjan van de Ven
2006-01-17 16:03       ` Alan Cox
2006-01-17 17:16         ` Kyle Moffett
2006-01-17 17:25         ` Dave Hansen
2006-01-18  4:54           ` Greg KH
2006-01-18  4:55           ` Greg KH
2006-01-18 16:23             ` Dave Hansen
2006-01-20 17:00               ` Eric W. Biederman
2006-01-20 20:18                 ` Hubertus Franke
2006-01-21 10:25                   ` Eric W. Biederman
2006-01-23 18:38                     ` Hubertus Franke
2006-01-23 18:48                       ` Eric W. Biederman
2006-01-21 14:42                   ` Eric W. Biederman
2006-01-22  6:43                     ` Kyle Moffett
2006-01-22 15:48                       ` Eric W. Biederman
2006-01-22 15:55                         ` Arjan van de Ven
2006-01-22 16:24                           ` Eric W. Biederman
2006-01-26 20:01                             ` Herbert Poetzl
2006-01-27  9:04                               ` Eric W. Biederman
2006-01-27 12:27                                 ` Kyle Moffett
2006-01-27 13:15                                   ` Eric W. Biederman
2006-01-23 18:50                     ` Hubertus Franke
2006-01-23 19:28                       ` Eric W. Biederman
2006-01-23 21:11                         ` Alan Cox
2006-01-23 21:30                           ` Eric W. Biederman
2006-01-23 22:15                             ` Hubertus Franke
2006-01-24  6:56                               ` Arjan van de Ven
2006-01-24 19:34                               ` Eric W. Biederman
2006-01-24 21:09                                 ` Hubertus Franke
2006-01-24  0:22                             ` Alan Cox
2006-01-24 19:26                               ` Eric W. Biederman [this message]
2006-01-24 21:11                                 ` Alan Cox
2006-01-24 21:15                                   ` Arjan van de Ven
2006-01-25  9:58                                     ` Eric W. Biederman
2006-01-25 15:10                                       ` Trond Myklebust
2006-01-25 18:01                                         ` Eric W. Biederman
2006-01-25 19:30                                           ` Trond Myklebust
2006-01-25 21:59                                             ` Eric W. Biederman
2006-01-25  9:13                                   ` Eric W. Biederman
2006-01-25  9:51                                   ` Eric W. Biederman
2006-01-26 20:23                                     ` Herbert Poetzl
2006-01-27  8:28                                       ` Eric W. Biederman
     [not found]                       ` <m1k6cqlmfe.fsf_-_@ebiederm.dsl.xmission.com>
2006-01-23 21:57                         ` RFC: [PATCH] pids as weak references Dave Hansen
2006-01-31 21:02                   ` RFC [patch 13/34] PID Virtualization Define new task_pid api Linus Torvalds
2006-02-01  0:01                     ` Hubertus Franke
2006-02-01  4:18                     ` Eric W. Biederman
2006-02-01  4:39                       ` Linus Torvalds
2006-02-01  7:14                         ` Eric W. Biederman
2006-02-01 16:41                         ` Dave Hansen
2006-02-02  5:14                         ` Herbert Poetzl
2006-02-01 16:29                       ` Greg
2006-02-01 16:44                         ` Eric W. Biederman
2006-02-02 13:50                           ` Greg
2006-02-02 14:09                             ` Eric W. Biederman
2006-02-02 14:48                     ` Kirill Korotaev
2006-02-02 15:13                       ` Eric W. Biederman
2006-02-02 15:26                         ` Kirill Korotaev
2006-02-02 15:51                           ` Eric W. Biederman
2006-02-02 16:05                             ` Kirill Korotaev
2006-02-02 16:27                               ` Eric W. Biederman
2006-02-02 21:32                                 ` Cedric Le Goater
2006-02-02 21:43                                   ` Hubertus Franke
2006-02-02 21:46                                   ` Eric W. Biederman
2006-02-03 10:07                                     ` Kirill Korotaev
2006-02-03 10:52                                 ` Kirill Korotaev
2006-02-03 11:09                                   ` Eric W. Biederman
2006-02-03 15:45                                   ` Dave Hansen
2006-02-03 16:35                                     ` Kirill Korotaev
2006-02-02 21:10                             ` Cedric Le Goater
2006-02-02 21:24                               ` Eric W. Biederman
2006-02-06 20:15                         ` Pavel Machek
2006-02-06 20:34                           ` Eric W. Biederman
2006-02-06 20:36                           ` Kirill Korotaev
2006-02-06 20:40                             ` Eric W. Biederman
2006-02-02 14:49           ` Kirill Korotaev
2006-01-17 14:33 ` RFC [patch 14/34] PID Virtualization const parameter for process group Serge Hallyn
2006-01-17 14:33 ` RFC [patch 15/34] PID Virtualization task virtual pid access functions Serge Hallyn
2006-01-17 14:33 ` RFC [patch 16/34] PID Virtualization return virtual pids where required Serge Hallyn
2006-01-17 14:33 ` RFC [patch 17/34] PID Virtualization return virtual process group ids Serge Hallyn
2006-01-17 14:33 ` RFC [patch 18/34] PID Virtualization code enhancements for virtual pids in /proc Serge Hallyn
2006-01-17 14:33 ` RFC [patch 19/34] PID Virtualization Define pid_to_vpid functions Serge Hallyn
2006-01-17 14:33 ` RFC [patch 20/34] PID Virtualization Use pid_to_vpid conversion functions Serge Hallyn
2006-01-17 14:33 ` RFC [patch 21/34] PID Virtualization file owner pid virtualization Serge Hallyn
2006-01-17 14:33 ` RFC [patch 22/34] PID Virtualization define vpid_to_pid functions Serge Hallyn
2006-01-17 14:33 ` RFC [patch 23/34] PID Virtualization Use " Serge Hallyn
2006-01-17 14:33 ` RFC [patch 24/34] PID Virtualization use vpgid_to_pgid function Serge Hallyn
2006-01-17 14:33 ` RFC [patch 25/34] PID Virtualization Context for pid_to_vpid conversition functions Serge Hallyn
2006-01-17 14:33 ` RFC [patch 26/34] PID Virtualization Documentation Serge Hallyn
2006-01-17 14:33 ` RFC [patch 27/34] PID Virtualization pidspace Serge Hallyn
2006-01-17 14:33 ` RFC [patch 28/34] PID Virtualization container object and functions Serge Hallyn
2006-01-17 14:33 ` RFC [patch 29/34] PID Virtualization container attach/detach calls Serge Hallyn
2006-01-17 14:33 ` RFC [patch 30/34] PID Virtualization /proc/container filesystem Serge Hallyn
2006-01-17 14:33 ` RFC [patch 31/34] PID Virtualization Implementation of low level virtualization functions Serge Hallyn
2006-01-17 14:33 ` RFC [patch 32/34] PID Virtualization Handle special case vpid return cases Serge Hallyn
2006-01-17 14:33 ` RFC [patch 33/34] PID Virtualization per container /proc filesystem Serge Hallyn
2006-01-17 14:33 ` RFC [patch 34/34] PID Virtualization pidspace parent : signal behavior Serge Hallyn
2006-01-17 16:19 ` RFC [patch 00/34] PID Virtualization Overview Suleiman Souhlal
2006-01-17 17:08   ` Dave Hansen
2006-01-17 18:09     ` Suleiman Souhlal
2006-01-17 18:12       ` Dave Hansen
2006-01-17 18:29         ` Alan Cox
2006-01-18 19:01           ` Dave Hansen
2006-01-18 19:28             ` Arjan van de Ven
2006-01-18 19:38               ` Dave Hansen
2006-01-18 19:50                 ` Arjan van de Ven
2006-01-18 22:54                 ` Alan Cox
2006-01-19  7:15                   ` Arjan van de Ven
2006-01-20  5:11                     ` Eric W. Biederman
2006-01-20 20:23                       ` Serge E. Hallyn
2006-01-20 20:33                         ` Hubertus Franke
2006-01-21 10:34                           ` Eric W. Biederman
2006-01-20 19:53                   ` RFC: Multiple instances of kernel namespaces Eric W. Biederman
2006-01-20 20:13                     ` Serge E. Hallyn
2006-01-20 20:22                       ` Hubertus Franke
     [not found]                         ` <20060120203555.GC13265@sergelap.austin.ibm.com>
2006-01-20 21:47                           ` Hubertus Franke
2006-01-21 10:04                       ` Eric W. Biederman
2006-01-26 19:47                         ` Herbert Poetzl
2006-01-26 20:13                           ` Eric W. Biederman
2006-01-26 20:27                             ` Herbert Poetzl
2006-01-21 10:31             ` RFC [patch 00/34] PID Virtualization Overview Pavel Machek

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