From owner-freebsd-bugs Wed Aug 25 15:11:40 1999 Delivered-To: freebsd-bugs@freebsd.org Received: from freefall.freebsd.org (freefall.FreeBSD.ORG [204.216.27.21]) by hub.freebsd.org (Postfix) with ESMTP id C7D3215335 for ; Wed, 25 Aug 1999 15:11:38 -0700 (PDT) (envelope-from gnats@FreeBSD.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.9.3/8.9.2) id PAA34411; Wed, 25 Aug 1999 15:10:03 -0700 (PDT) (envelope-from gnats@FreeBSD.org) Date: Wed, 25 Aug 1999 15:10:03 -0700 (PDT) Message-Id: <199908252210.PAA34411@freefall.freebsd.org> To: freebsd-bugs@FreeBSD.org Cc: From: Bruce Evans Subject: Re: kern/11736: On fast machines kernel reports negative i586_bzero bandwith values due to datatype overflow Reply-To: Bruce Evans Sender: owner-freebsd-bugs@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org The following reply was made to PR kern/11736; it has been noted by GNATS. From: Bruce Evans To: bde@freebsd.org, freebsd-gnats-submit@freebsd.org, sobomax@altavista.net Cc: Subject: Re: kern/11736: On fast machines kernel reports negative i586_bzero bandwith values due to datatype overflow Date: Thu, 26 Aug 1999 08:01:11 +1000 >It seems that all OK now, so you can close this PR. I don't think I actually fixed it. The problem is that the test is run before interrupts are enabled, so the i8254 clock overflows after 10 msec. I fixed overflow detection, so the clock is accurate for up to 20 msec depending on when the test is started. The test writes 10^6 bytes which normally takes 5-10 msec on a P5 (it takes about 6 msec on my P5/133). However, K6-1's at least are slower (the test takes about 12 msec on my K6-1/233), so there is some chance of it not working. Possible fixes: 1) always use the TSC for timing the test. 2) use a smaller buffer and be more careful about caching. The test should be more careful about caching anyway. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message