Date: Tue, 03 Apr 2001 04:05:31 -0700 From: Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca> To: Bert Driehuis <driehuis@playbeing.org> Cc: "Jason T. Luttgens" <lucky@lansters.com>, freebsd-stable@FreeBSD.ORG Subject: Re: Network performance question Message-ID: <200104031106.f33B6PA02869@cwsys.cwsent.com> In-Reply-To: Your message of "Tue, 03 Apr 2001 01:18:42 %2B0200." <Pine.BSI.4.21.0104030111410.5679-100000@c1111.nl.compuware.com>
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In message <Pine.BSI.4.21.0104030111410.5679-100000@c1111.nl.compuware.c om>, Be rt Driehuis writes: > On Mon, 2 Apr 2001, Jason T. Luttgens wrote: > > > However - I noticed something while testing. Linux 2.4.3 did not access the > > drive as much as FreeBSD was. I guess Linux is caching the file more or > > something...who knows. So I re-performed the tests with output going to > > /dev/null and looking at the tcpdump and interface counters (I know, it's > > not the best way, but at this point I was thinking it's the disk I/O that's > > causing the drops/loss). > > You could try enabling softupdates if you haven't done so yet. For > benchmarking purposes, you could also try async mount (but note that > async can screw up your disk real bad in case of a system crash). If you want to make all things as equal as possible, you will have to mount async. According to Kirk's paper on Softupdates, Softupdates was about 3% slower than async mounts and a lot faster than SMD mounts. Does anyone on this list have a pointer to the paper so I could reread it? Would it be possible to include it in /usr/share/doc/papers? > > I would not expect either to have much effect if the machine is > otherwise quiescent, but if you are being hit because of any synchronous > activity going on it would be nice if this could be eliminated from the > equation. Depending on how heavy the traffic was at the time you were capturing packets I would think that softupdates or async mounts would have made a big difference. > > Note that you really are entering a grey area here -- it may well be > that the respective kernels have different priorities or strategies that > have little to do with Ethernet performance, e.g. FreeBSD's insistence > (by default) that file systems remain consistent in case of a system > crash might cause some packets to be lost in this flat out. worst case > scenario. It is unlikely that you will prove what happens unless you > stumble upon something that eliminates the difference. Until we have a level playing field, it's a comparison between apples and oranges. Regards, Phone: (250)387-8437 Cy Schubert Fax: (250)387-5766 Team Leader, Sun/Alpha Team Internet: Cy.Schubert@osg.gov.bc.ca Open Systems Group, ITSD, ISTA Province of BC To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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