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Date: Sun, 6 Mar 2005 03:11:24 -0500 (EST)
From: Jeff Roberson <jroberson@chesapeake.net>
To: David Xu <davidxu@FreeBSD.org>
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References: <200503050915.j259F30c058488@repoman.freebsd.org>
 <20050305041220.M4921@odysseus.silby.com> <422A46E3.6070902@freebsd.org>
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cc: cvs-src@FreeBSD.org
cc: Mike Silbersack <silby@silby.com>
cc: src-committers@FreeBSD.org
cc: cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/sys proc.h umtx.h src/sys/kernkern_thread.c
 kern_umtx.c
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On Sun, 6 Mar 2005, David Xu wrote:

> Mike Silbersack wrote:
>
> >
> > On Sat, 5 Mar 2005, David Xu wrote:
> >
> >> davidxu     2005-03-05 09:15:03 UTC
> >>
> >>  FreeBSD src repository
> >>
> >>  Modified files:
> >>    sys/sys              proc.h umtx.h
> >>    sys/kern             kern_thread.c kern_umtx.c
> >>  Log:
> >>  Allocate umtx_q from heap instead of stack, this avoids
> >>  page fault panic in kernel under heavy swapping.
> >
> >
> > Heavy swapping, or just unlucky swapping like we were talking about in
> > relation to kern_sig.c?
> >
> If I understand it correctly, kernel stack is swapped out only when
> there is memory
> pressure, for example, following code:
>
> char  *p = malloc(1024 * 1024 * 512); // assume you have memory less
> than 512M
> for (;;)
>     memset(p, 0, 1024 * 1024 * 512);
>
> and if there is thousands of thread in the kernel and all are sleeping
> (rarely extreme case), swapping out all their kernel stack can save several
> megabytes. because so many people have the objection to disable it, and
> would like to accept a serious risk, I just adjusted the code to work
> around it,
> that does not mean I agree their points.



>
> > Mike "Silby" Silbersack
> >
> >
>