some question about kernel and user mode!

Jincuteguy · Sep 21, 2003, 06:13 PM

Let say I have a function write_block(...) which must be run in supervisor (kernel) mode. What type of differences will I see when a user process versus a supervisor process needs to invoke write_block? Consider both how a programmer might invoke write_block and any differences in performance. Thx

Jincuteguy · Sep 22, 2003, 05:46 AM

anyone???

Jincuteguy · Sep 22, 2003, 05:46 AM

Let say I have a function write_block(...) which must be run in supervisor (kernel) mode. What type of differences will I see when a user process versus a supervisor process needs to invoke write_block? Consider both how a programmer might invoke write_block and any differences in performance. Thx

ToshiroOC · Sep 22, 2003, 08:33 AM

You don't need two different threads, merged. And sorry to say, but this above my head, otherwise I would have answered. There are some windows gurus on here, just wait and hopefully one can help you with your question.

Andrew275 · Sep 22, 2003, 10:03 PM

It's been a while since I messed with this stuff, but I don't think it would be a major performance problem. For example, they moved the graphics subsystem to kernel mode in Windows to improve performance. And if the function requires supervisor privileges anyway, there's no way around it. It probably would run a bit faster if it was being called from a kernel mode process, however.

Jincuteguy · Sep 23, 2003, 04:57 AM

Does a user process or supervisor (kernel ) process have higher performance? also how are they differeces in performance? thx.

Jeff · Sep 23, 2003, 06:45 AM

Merged threads, this is the third thread you started regarding the same subject, please keep the discussion in the one thread!

UberLord · Sep 23, 2003, 11:03 AM

Quote:

Originally posted by Jincuteguy
Does a user process or supervisor (kernel ) process have higher performance? also how are they differeces in performance? thx.

Hard to measure really.
Someone wrote a kernel-space HTTP server for linux, but a userspace FTP server called vsftpd was still able to send data much faster. Different protocols I know - but speed it gained by optimising the code, not where it runs.

Running in kernel space, the process has full access to everything and can pull the entire system down.
Running in user space, the process has controllable access and it's much harder (but still possible) to pull the system down.

Basically unless you're talking directly to hardware (ie a driver) you have no reason to be writing a kernel program

Sep 21, 2003, 06:13 PM	#1
Jincuteguy DriverHeaven Lover Join Date: May 2003 Posts: 200 Rep Power: 0	some questions about kernel and user mode!!! Let say I have a function write_block(...) which must be run in supervisor (kernel) mode. What type of differences will I see when a user process versus a supervisor process needs to invoke write_block? Consider both how a programmer might invoke write_block and any differences in performance. Thx

Sep 22, 2003, 05:46 AM	Thread Starter #3
Jincuteguy DriverHeaven Lover Join Date: May 2003 Posts: 200 Rep Power: 0	some question about kernel and user mode! Let say I have a function write_block(...) which must be run in supervisor (kernel) mode. What type of differences will I see when a user process versus a supervisor process needs to invoke write_block? Consider both how a programmer might invoke write_block and any differences in performance. Thx

Sep 22, 2003, 08:33 AM	#4
ToshiroOC Unbiased. Join Date: Jun 2002 Posts: 4,812 Rep Power: 0	You don't need two different threads, merged. And sorry to say, but this above my head, otherwise I would have answered. There are some windows gurus on here, just wait and hopefully one can help you with your question. __________________ [img][/img] [color=White]Peace be with you, Joe.[/color] Driverheaven Staff Member (Supermoderator)

Sep 23, 2003, 04:57 AM	Thread Starter #6
Jincuteguy DriverHeaven Lover Join Date: May 2003 Posts: 200 Rep Power: 0	kernel vs user processes! Does a user process or supervisor (kernel ) process have higher performance? also how are they differeces in performance? thx.

Sep 23, 2003, 06:45 AM	#7
Jeff Yarr... I be blind! Join Date: May 2002 Location: Calgary, Canada Posts: 3,191 Rep Power: 80	Merged threads, this is the third thread you started regarding the same subject, please keep the discussion in the one thread! __________________

Sep 22, 2003, 05:46 AM	Thread Starter #2
Jincuteguy DriverHeaven Lover Join Date: May 2003 Posts: 200 Rep Power: 0	anyone???

Sep 22, 2003, 10:03 PM	#5
Andrew275 Custom User Title Join Date: May 2002 Location: Washington Posts: 1,125 Rep Power: 0 System Specs	It's been a while since I messed with this stuff, but I don't think it would be a major performance problem. For example, they moved the graphics subsystem to kernel mode in Windows to improve performance. And if the function requires supervisor privileges anyway, there's no way around it. It probably would run a bit faster if it was being called from a kernel mode process, however.