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Re: updating COMPAT_LINUX for linux 2.6.x support (take 2)
On Thu, Jun 17, 2010 at 12:07:43PM -0400, Matthew Mondor wrote:
> On Thu, 17 Jun 2010 10:25:59 +0000
> Andrew Doran <ad%NetBSD.org@localhost> wrote:
> > This is mainly down the fact that we need kernel_lock to bracket "legacy"
> > sections of code that aren't preemption safe. I think MULTIPROCESSOR
> > should be sent off to the glue factory but that's another discussion :-).
> Is there any way that performance for the uniprocessor case could be
> preserved, where some synchronization/preemption-safe blocks are
> unnecessary, without having conditional code when MULTIPROCESSOR?
Generally speaking, performance for the uniprocessor case is, in fact,
preserved, because the actual bus-locking operations are patched away
at startup time.
However, only x86 currently supports this, I believe. Very similar code
is required by part of DTrace (FBT) and I wish someone had both the time
and the skills to work on it for more architectures. But that's not me.
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