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Old 01-12-2011, 11:39 AM   #1
aggrishabh
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process id 0


Hi All,

Can someone shed some light on the role of process id 0 in linux. i know this process is for scheduler, but what this process do.

Please correct me if i am wrong.
 
Old 01-12-2011, 11:41 AM   #2
fbsduser
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IIRC. ID 0 is init.
 
Old 01-12-2011, 11:21 PM   #3
aaaaatoz
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Quote:
Originally Posted by fbsduser View Post
IIRC. ID 0 is init.
I am confused whether init's PID is 0 or 1 ?
 
Old 01-12-2011, 11:26 PM   #4
TheIndependentAquarius
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Quote:
Originally Posted by aaaaatoz View Post
I am confused whether init's PID is 0 or 1 ?
Also do a man init
Code:
anisha@linux-uitj:~>ps -el
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
4 S     0     1     0  0  80   0 -  2018 poll_s ?        00:00:00 init
1 S     0     2     0  0  75  -5 -     0 kthrea ?        00:00:00 kthreadd
1 S     0     3     2  0 -40   - -     0 migrat ?        00:00:00 migration/0
1 S     0     4     2  0  75  -5 -     0 ksofti ?        00:00:04 ksoftirqd/0
5 S     0     5     2  0 -40   - -     0 watchd ?        00:00:00 watchdog/0 
1 S     0     9     2  0  75  -5 -     0 worker ?        00:00:00 events/0   
1 S     0    11     2  0  75  -5 -     0 worker ?        00:00:00 khelper    
1 S     0    12     2  0  75  -5 -     0 worker ?        00:00:00 netns      
1 S     0    13     2  0  75  -5 -     0 async_ ?        00:00:00 async/mgr  
1 S     0    14     2  0  75  -5 -     0 worker ?        00:00:00 kintegrityd/0
1 S     0    16     2  0  75  -5 -     0 worker ?        00:00:00 kblockd/0    
...
0 S  1000  6566  5281  0  80   0 -  3472 wait   pts/3    00:00:00 bash
0 R  1000  6587  6566  0  80   0 -  1139 -      pts/3    00:00:00 ps
0 S  1000  9750  5354  0  80   0 - 163619 poll_s pts/0   00:03:51 qtcreator
...
0 S  1000 16742  5281  0  80   0 -  3500 n_tty_ pts/2    00:00:00 bash
 
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Old 01-13-2011, 02:01 AM   #5
divyashree
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Quote:
Originally Posted by aggrishabh View Post
Hi All,

Can someone shed some light on the role of process id 0 in linux. i know this process is for scheduler, but what this process do.

Please correct me if i am wrong.
swapper or sched has process ID 0 and is responsible for paging during kernel initialization.

Last edited by divyashree; 01-13-2011 at 02:05 AM.
 
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Old 01-13-2011, 02:21 AM   #6
TheIndependentAquarius
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and putting the following keywords in Google will yield more results:
Quote:
Linux scheduler pid
 
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Old 01-14-2011, 07:40 AM   #7
archtoad6
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My compliments on the way you suggested Google keywords -- nice phrasing, helpful, & polite.
 
Old 01-14-2011, 08:41 AM   #8
TheIndependentAquarius
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Well, thank you, I could have given the OP link too but I wanted him to know how to form appropriate keywords to get the desired results from Google.
 
Old 01-14-2011, 08:47 AM   #9
resetreset
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Quote:
Originally Posted by divyashree View Post
swapper or sched has process ID 0 and is responsible for paging during kernel initialization.
Can you expound on this a bit?


What do you mean swapper OR sched? And what do you mean "paging during kernel initialization"?

Last edited by resetreset; 01-14-2011 at 08:49 AM.
 
Old 01-14-2011, 08:52 AM   #10
deeh514
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@Anisha....i think it's time for a link :P
 
Old 01-14-2011, 09:28 AM   #11
TheIndependentAquarius
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Quote:
Originally Posted by deeh514 View Post
@Anisha....i think it's time for a link :P
Welcome to LQ!
 
Old 01-16-2011, 04:52 AM   #12
resetreset
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thanks, but I still don't get what "paging during kernel initialization" is.....
 
Old 01-17-2011, 01:01 AM   #13
divyashree
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Quote:
Originally Posted by resetreset View Post
thanks, but I still don't get what "paging during kernel initialization" is.....
Do you know what is paging ? Please google for details. Its a beautiful memory mgmt. technique used by the kernel.

Our primary memory is divided into some logical blocks of same size called pages, by the kernel.

swapper or sched is the swapper daemon which swaps processes from primary memory to swap area(virtual memory) whenever needed i.e to free the pages from primary memory. And during kernel initialization, kernel starts the swapper daemon(sched) to do this.
 
Old 01-19-2011, 01:03 AM   #14
resetreset
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I am extremely well aware what paging is. There is no "paging during kernel initialization" - the x86 *chip* will simply take addresses that are not in RAM, and the kernel has to bring that data off the disk. This whole thing is activated when the chip is put into Protected Mode, it's not the *kernel* which does anything.
 
Old 01-19-2011, 02:46 AM   #15
syg00
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Hmmmm.
Swapper has nothing to do with (modern) swap. In fact process swap-out in Linux hasn't existed for years. kswapd manages pages to swap.
The kernel doesn't page, although it does have page table built for it - by "swapper/process 0" I believe. Who knows where the name came from originally.
 
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