lkml.org 
[lkml]   [1999]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE:RE: [OFFTOPIC] Re: Linux Kernel constraints!
Date
Please reply directly bcoz i am currently not on linux-kernel mailing list.
Please water the flames bcoz as an os nt is not bad (what with VMS as its
base?)!

[snip]
>On Sat, 23 Jan 1999, pleXus wrote:
>Excuse me? When a process calls a system call, the process is running _in
>the kernel_ (see below). Multiple processes can call the same system
>calls. If the machine is SMP, two processes can call the same system call
>simultaneously. What, pray tell, is your definition of reentrant?

i think author didnot mean processes in wait state.

> >> 3. kernel is not multi processing in the sense that on multiprocessor
> >> systems it will run on only one cpu at a time.
> >
> >And this is even more absurd. SMP is _symmetric_. Kernel runs on all
> >processors _by definition_. There may be some confusion here with
respect
> >to lock granularity though. The very first SMP kernels had a single lock
> >that protected most data structures, which drastically limited kernel
> >concurrency. Current kernels have more fine-grained locking that allow
> >much better concurrency and therefore better scaling.

that was precisely the doubt i had. which were cleared on list earlier that
for most of funcitons now 2.2version has finer grained locks. some places
like in network control still single lock exists so may not show good
concurrency but lower latency times overall prevent any of these from being
a limitation per se.

>>
>> Can someone more knowledgeable explain to me whether or not the KERNEL
runs
>> on more than one processor.. I am curious, because that would be
>> interesting to hear.
>
>The kernel is more like a library than a process. Calling the kernel is
>not a task switch - it's just a fancy function call (a software interrupt
>that does a ring 0 transition). Task switches happen when schedule()
[snip]
>sometimes one processor will have to spin its wheels waiting to access
>something, but this is no different from NT.
>
>But don't take my word for it, look at the source.

what about the kernel threads? what all core processes/threads are needed
for process and device management apart from Scheduler? could someone
please throw light on it.

does linux have kernel multithreads, instead of just user multithreads,
some thing like light weight processes on Solaris (each process can have
multiple kernel threads to schedule on and multiple user threads to perform
tasks).

yogi



-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:49    [W:1.589 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site