Date: Thu, 14 Jan 1999 20:08:32 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: "Robert V. Baron" <rvb@cs.cmu.edu> Cc: "Ron G. Minnich" <rminnich@Sarnoff.COM>, zhihuizhang <bf20761@binghamton.edu>, hackers <freebsd-hackers@FreeBSD.ORG> Subject: Re: TSS and context switch Message-ID: <199901150408.UAA28638@apollo.backplane.com>
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:"Ron G. Minnich" <rminnich@Sarnoff.COM> writes:
:
:> I'm assuming you measured all this and determined that TSS was faster?
:>
:> Ron
:Let's make it simpler for him. Why don't you just let him look
:in the architecture manual for the 386/486/586 and PII and see
:how many cycles the load and save takes compared to what is done
:in practice.
The Intel TSS stuff is *extremely* *slow* compared to doing it
with discrete instructions, especially since many of the major
supervisory registers do not change.
There are a number of intel instructions which were designed to
run fast on a 486, which turn out to be dogs on higher-end cpu's.
For example, the ENTER instruction is considerably slower then
doing the frame pointer / stack pointer manipulation manually.
There are many others.
-Matt
Matthew Dillon
<dillon@backplane.com>
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