Date: Thu, 15 Feb 1996 09:17:31 -0500 (EST) From: "Ron G. Minnich" <rminnich@Sarnoff.COM> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: hackers@FreeBSD.org Subject: Re: Paging questions Message-ID: <Pine.SUN.3.91.960215090347.14306B-100000@terra> In-Reply-To: <199602151302.OAA07491@labinfo.iet.unipi.it>
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> More questions/thoughts on paging support for small-memory system. > First, a preliminary question: > How expensive is it to get a page fault which immediately > returns without doing anything (lets call this a Quick Fault) OK, i did a test of this on a p90. If you short stop the trap code in i386/i386/trap.c and just return on a user fault from a page fault it happens in about 4 microseconds on a p90, fbsd 2.05R, neptune chipset. IF you do much more, and in particular if pmap_unuse_pt gets called, it goes to more like 100. ron
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