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Date:      Tue, 1 May 2001 12:57:44 +1000 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        John Baldwin <jhb@FreeBSD.ORG>
Cc:        Alfred Perlstein <bright@wintelcom.net>, smp@FreeBSD.ORG, Jake Burkholder <jburkholder0829@home.com>
Subject:   Re: that vm diff now makes it into single user mode.
Message-ID:  <Pine.BSF.4.21.0105011221040.31299-100000@besplex.bde.org>
In-Reply-To: <XFMail.010430120119.jhb@FreeBSD.org>

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On Mon, 30 Apr 2001, John Baldwin wrote:

> On 29-Apr-01 Alfred Perlstein wrote:
> > * Jake Burkholder <jburkholder0829@home.com> [010428 23:10] wrote:
> >> 
> >> i386/i386/vm_machdep.c:
> >> 
> >> the mtx_trylock in vm_page_zero_idle is unnecessary, the lock is
> >> already held.  This whole thing needs to be non-blocking if its
> >> going to be called from the idle loop, but I'm not sure that
> >> that's still possible.  Its currently commented out.
> > 
> > Ok, should be fixed.  I guess we now know where it could have been
> > useful to be able to spin on a sleeplock, ie not worry about
> > idle getting stuck on a runqueue/sleepqueue.
> 
> Having the idle process hold locks that other threads block on can really start
> wreaking havoc when you throw priority propagation into the mix.  It would be
> best to push the page zeroing off into a very low priority kernel thread or
> something.

Why would that do more than move the problem (if any)?  Priority
propagation should allow the low-priority idle process to become high
prority so that it can release its locks as necessary just as well as
it allows this for any other low-priority process.

Bruce


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