Date: Thu, 15 Aug 2002 22:16:09 -0700 From: David Greenman-Lawrence <dg@dglawrence.com> To: David Greenman <dg@FreeBSD.org> Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern uipc_socket2.c Message-ID: <20020815221609.E42978@nexus.root.com> In-Reply-To: <200208160508.g7G58kRZ098250@freefall.freebsd.org>; from dg@FreeBSD.org on Thu, Aug 15, 2002 at 10:08:46PM -0700 References: <200208160508.g7G58kRZ098250@freefall.freebsd.org>
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>dg 2002/08/15 22:08:46 PDT > > Modified files: > sys/kern uipc_socket2.c > Log: > Rewrote the space check algorithm in sbreserve() so that the extremely > expensive (!) 64bit multiply, divide, and comparison aren't necessary ... > The 64bit math in this function was measured in some kernel profiles as > being as much as 5-8% of the total overhead of the TCP/IP stack and I'm looking at calcru() as well, since is does four 64bit divides and was as expensive as sbreserve() in my profiles. The __qdivrem function that does the 64bit divide appears to consume several thousand instructions in the common case. Something to avoid if at all possible. -DG D.G.Lawrence Download Technologies, Inc. - http://www.downloadtech.com - (866) 399 8500 TeraSolutions, Inc. - http://www.terasolutions.com - (503) 288 9544 The FreeBSD Project - http://www.freebsd.org Pave the road of life with opportunities. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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