Date: Tue, 15 Mar 2005 22:19:43 -0500 From: Stephan Uphoff <ups@tree.com> To: Peter Wemm <peter@wemm.org> Cc: "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org> Subject: Re: Removing kernel thread stack swapping Message-ID: <1110943183.29804.42558.camel@palm> In-Reply-To: <200503151743.49851.peter@wemm.org> References: <20050303074242.GA14699@VARK.MIT.EDU> <20050303153505.GA16964@VARK.MIT.EDU> <200503151743.49851.peter@wemm.org>
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On Tue, 2005-03-15 at 20:43, Peter Wemm wrote: > On Thursday 03 March 2005 07:35 am, David Schultz wrote: > > On Thu, Mar 03, 2005, John Baldwin wrote: > [..] > > > Hence, don't kill this whole feature just because someone is too > > > lazy to fix a bug. > > > > Fair enough. I'll defer to you on the extent of the problem. > > David seemed to think that it was more widespread. (BTW, does > > *anyone* know what the PHOLD() in kern_physio is for? Is it a > > holdover from when the PCB was in struct user?) > > I've wondered about this myself in the past. I went looking once and > discovered that it never did anything that I could find. I believe it > is a case of 'because it was always done that way' or because the > pseudocode in the Bach or bsd books had it. There is certainly no > functional need for it in FreeBSD. kern_physio prevents chunks of memory needed for IO from being paged out. Swapping out a thread in kern_physio will prevent it from releasing the resources soon. With minphys > stack size I think PHOLD() is still a good idea. Stephan
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