Pavel Emelianov <[EMAIL PROTECTED]> writes:
> [EMAIL PROTECTED] wrote:
>> Pavel Emelianov [EMAIL PROTECTED] wrote:
>> | This patch opens the flat model patches.
>> |
>> | The flat model idea is that struct pid has two numbers. The first one
>> | (pid->nr) is a global one and is unique in the system. The second one
>> | (pid->vnr) is a virtual pid. It is used on the kernel user boundary only.
>>
>> This approach duplicates 5 integers and 2 pointers per process for every
>> process in the system. While this may not be expensive for processes that
>> actually use multiple namespaces, doesn't it waste memory if majority of
>> processes exist only in one namespace ?
>
> task_struct alignment allows for it. so does the alignment of signal
> structure.
> and please note that this comes with appropriate ifdefs around. the only
> problem
> is with struct pid, but we're virtualizing it after all!
>
> moreover - two integers and a pointer to the namespace is the minimal set of
> fields for pid that is visible from two namespaces...
>> | --- ./include/linux/sched.h.flatdatast 2007-06-15 15:14:33.000000000 +0400
>> | +++ ./include/linux/sched.h 2007-06-15 15:19:14.000000000 +0400
>> | @@ -482,7 +482,10 @@ struct signal_struct {
>> | pid_t session __deprecated;
>> | pid_t __session;
>> | };
>> | -
>> | +#ifdef CONFIG_PID_NS_FLAT
>> | + pid_t vpgrp;
>> | + pid_t vsession;
>> | +#endif
>> | /* boolean value for session group leader */
>> | int leader;
>> |
>> | @@ -944,6 +947,11 @@ struct task_struct {
>> | unsigned did_exec:1;
>> | pid_t pid;
>> | pid_t tgid;
>> | +#ifdef CONFIG_PID_NS_FLAT
>> | + /* hash the virtual ids as well */
>> | + pid_t vpid;
>> | + pid_t vtgid;
>> | +#endif
Adding vpgrp, vsession, vpid, and vtgid is wrong.
A case can probably be made for caching the common case (users view),
but we already have fields for that.
For a global view we must use struct pid *, otherwise we are just asking
for trouble.
Eric
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