Messages in this thread | | | From | Rajib Chakma <> | Subject | RE:RE: [OFFTOPIC] Re: Linux Kernel constraints! | Date | Tue, 24 Mar 1998 16:51:40 -0000 |
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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
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