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List:       linux-smp
Subject:    Re: LOCKING/IRQ IN SMP 2.2
From:       Ingo Molnar <mingo () chiara ! csoma ! elte ! hu>
Date:       1999-09-25 9:55:26
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On Sat, 25 Sep 1999, Subscriber wrote:

> I have two simple (i think so) questions about differencies between
> Linux 2.2 and 2.0:
> 1. Are IRQs handled directly by additional processors (not via IPI)?

yes, we fully utilize IOAPIC(s) if available, they deliver IRQs directly
to all CPUs, without doing IPI redirection.

> 2. Could be more than one processor in kernel mode (for example:
> parallel processing of system calls)?

yes. Parts of the 2.2 kernel still used the 'big kernel lock'. In the 2.3
kernels the usage of the big kernel lock has basically disappeared, all
major Linux kernel subsystems are fully threaded: networking, VFS, VM, IO,
block/page caches, scheduling, interrupts, signals, etc.

-- mingo

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