Date: Mon, 24 Jun 2002 14:57:59 -0600 (MDT) From: "M. Warner Losh" <imp@village.org> To: winter@jurai.net Cc: phk@critter.freebsd.dk, arch@FreeBSD.ORG Subject: Re: It is time to admit that removable devices exist Message-ID: <20020624.145759.95908168.imp@village.org> In-Reply-To: <20020624164822.H95270-100000@sasami.jurai.net> References: <83073.1024951336@critter.freebsd.dk> <20020624164822.H95270-100000@sasami.jurai.net>
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In message: <20020624164822.H95270-100000@sasami.jurai.net>
"Matthew N. Dodd" <winter@jurai.net> writes:
: I want to see the performance hit this causes quantified on lower end
: hardware before drivers are patched to support this API (which I concede
: may have some use outside PCMCIA devices.)
The cost on low end machines (where you have nexus -> isa -> device)
is going to be 3 indirect function calls per call for the non pccard
case, which is << 1us cycle time of the ISA bus. 3 indirect function
calls would be on the order of 25-100 cycles depending on the CPU.
For all but the slowest of hardware no one will notice this extra
processing. Even on a 33MHz 386 this would be only about 3us. I
doubt I could measure its effect on anything faster than a P90 or
P100.
Warner
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