Date: 17 Dec 1997 19:13:24 +0100 From: Eivind Eklund <perhaps@yes.no> To: dyson@FreeBSD.ORG Cc: garbanzo@hooked.net (Alex), current@FreeBSD.ORG Subject: Re: Pentium optimizations Message-ID: <86pvmvaldn.fsf@bitbox.follo.net> In-Reply-To: "John S. Dyson"'s message of Wed, 17 Dec 1997 01:23:22 -0500 (EST) References: <199712170623.BAA00476@dyson.iquest.net>
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"John S. Dyson" <dyson@FreeBSD.ORG> writes: > I do have some PPro mods, and they appear to help performance on > average. The PPro is a really wierd creature (like the K6.) The > darned processor does so much optimization, it appears to be > insensitive to code mods. There are areas of reasonable payoffs, > and lots of "obvious" optimizations that end up being neutral. I was working with optimizing assembly code for the PPro a year ago. My experience was that modifying code seldom mattered, except for alignement. Making the tight loops hit 16-byte boundaries roughly doubled the speed. No other approach made a significant difference, AFAIR (I just supplied ideas and had another programmer implement them). All pairing happened automatically, and touching the cache to make it pre-fetch etc didn't help at all. Eivind.
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