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Date:      Thu, 14 Dec 2000 13:16:09 +0100 (CET)
From:      Marius Bendiksen <mbendiks@eunet.no>
To:        Matt Dillon <dillon@earth.backplane.com>
Cc:        Julian Elischer <julian@elischer.org>, Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp>, arch@FreeBSD.ORG
Subject:   Re: Even 1GB KVA is not enough, but we have no more space
Message-ID:  <Pine.BSF.4.05.10012141314080.43757-100000@login-1.eunet.no>
In-Reply-To: <200012140655.eBE6tmP92001@earth.backplane.com>

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>     We're probably not going to ever do anything like this, because
>     manipulating page directory entries or the whole VM space on a 
>     user->supervisor or supervisor->user transition flushes
>     the TLB and seriously degrades performance.

Hence my reference to doing this on-demand. If the kernel could be taught
about virtual/physical paging issues (ie. could be aware of whether objects
are currently in the KV space), then you could avoid this except in the few
cases where you hit the 1G limit.

Marius



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