Date: Wed, 28 Nov 2001 13:16:41 -0800 From: Peter Wemm <peter@wemm.org> To: Luigi Rizzo <luigi@FreeBSD.org> Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/pci if_sis.c Message-ID: <20011128211641.5FF9E3808@overcee.netplex.com.au> In-Reply-To: <200111281610.fASGAcU63381@freefall.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
Luigi Rizzo wrote: > luigi 2001/11/28 08:10:37 PST > > Modified files: > sys/pci if_sis.c > Log: > Remove the need for an expensive m_devget on the i386, which does not > have alignment problems. Yes it does, just not fatal ones. Different models of the x86 family have different characteristics doing these. > On small boxes (e.g. the net4501 from Soekris, featuring a 486/133) > this provides huge performance benefits: the peak forwarding rate > with avg.sized packets goes up by 50-70% because of this change > alone. Faster CPUs might benefit less from this change, but in any > case the CPU has better things to do than waste time on useless > memory-to-memory copies. While this helps things like packet forwarding, it hurts things like NFS which now have to do lots and lots of unaligned accesses. Have you benchmarked anything else besides packet forwarding? > Right now the new behaviour is controlled by a sysctl variable, > hw.sis_quick which defaults to 1 (on), you can set it to 0 to > reintroduce the old behaviour (and compare the results). The > variable is only there to show how much you can gain with this > change, it will go away soon. Please do not remove this yet. Cheers, -Peter -- Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au "All of this is for nothing if we don't go to the stars" - JMS/B5 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20011128211641.5FF9E3808>