Date: Thu, 10 Jul 2003 15:37:34 +0000 From: Bosko Milekic <bmilekic@technokratis.com> To: "Alan L. Cox" <alc@imimic.com> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern subr_param.c sys_pipe.c src/sys/sys pipe.h Message-ID: <20030710153734.GA1101@technokratis.com> In-Reply-To: <3F0DBC39.891A91A@imimic.com> References: <200307080457.h684vRM7009343@gw.catspoiler.org> <20030708000257.D6158@odysseus.silby.com> <20030708004340.T6733@odysseus.silby.com> <3F0B199E.A3C980D2@imimic.com> <20030710182436.GA6484@HAL9000.homeunix.com> <3F0DBC39.891A91A@imimic.com>
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On Thu, Jul 10, 2003 at 02:19:21PM -0500, Alan L. Cox wrote: [...] > > That would alleviate the KVA pressure, since the mapping would be > > very temporary and you could even get away with just a single > > page. However, it would still tie up the associated physical > > memory until the pipe is read, which may not be soon at all. Is > > there a reason for the memory to be wired, other than that the > > data is easier to track down while the sending process' PTEs are > > still there? I would expect that you could instead just look up > > the appropriate vm_object and lazily fault in the appropriate pages > > on the receiver's side, modulo a few details such as segfault handling. > > But perhaps I'm missing something... > > It's a matter of priorities. With the growth trend in physical memory > sizes (and PAE), I see more problems due to KVA pressure than > unnecessarily wired memory. A recent, and fairly visible example, was > the vnode autosizing problems that had to be fixed prior to 5.1-RELEASE. With the recent bug reporting regarding kmem_map being too small coming in, I'd have to say that I agree with that assertion. Address space has become more expensive than memory, at least on ia32, and it's gotten to the point where we need to re-evaluate some of our autosizing and max size constants (for example, see VM_KMEM_SIZE_MAX). > Regards, > Alan Regards, -- Bosko Milekic * bmilekic@technokratis.com * bmilekic@FreeBSD.org TECHNOkRATIS Consulting Services * http://www.technokratis.com/
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