Date: Tue, 21 Feb 2006 08:37:37 -0800 (PST) From: Donald Baud <donaldbaud@yahoo.com> To: Luigi Rizzo <rizzo@icir.org> Cc: freebsd-ipfw@freebsd.org Subject: Re: Patch to add burst to dummynet ? Message-ID: <20060221163737.31550.qmail@web37411.mail.mud.yahoo.com> In-Reply-To: <20060221082529.B64136@xorpc.icir.org>
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> > > > --- Luigi Rizzo <rizzo@icir.org> wrote: > > > ... > > > > > of course you get the same throughput! > > > > > the burst is just a constant in the time it > > > takes to > > > > > transfer data, > > > > > and it is independent of the data size. > > > irrespective > > > > > of the file > > > > > size you'll just finish > (burst_size/bandwidth) > > > > > seconds earlier. > > > > > > > > > > cheers > > > > > luigi > > > > > > > > I ran two tests with the following ipfw rules: > > > > ipfw pipe 10 config bw 10kbit/s > > > > ipfw add 5 pipe 10 ip from 10.0.0.1 to me > > > > == with: if (len_scaled > q->numbytes) == > > > > wget --progress=dot some_file > > > > 0K .......... .......... 0% 1.13 KB/s > > > > 50K .......... .......... 1% 1.14 KB/s > > > > 100K .......... .......... 2% 1.14 KB/s > > > > 150K .......... .......... 3% 1.14 KB/s > > > > > > > > == with: if (len_scaled > q->numbytes + 100000 > ) > > > > wget --progress=dot some_file > > > > 0K .......... .......... 0% 1.13 KB/s > > > > 50K .......... .......... 1% 1.14 KB/s > > > > 100K .......... .......... 2% 1.14 KB/s > > > > 150K .......... .......... 3% 1.14 KB/s > > > > > > > > and so ? as i said, the throughtput is the same, > you > > > just see things happening a little bit (very > little, > > > usually) earlier, > > > and your experiment has no notion of time, and > > > furthermore there are so many factors > influencing > > > the throughput and the numbers printed by wget > > > that it's hard to tell how can you see the > > > difference. > > > > > > assuming, of course, that the patch i suggested > > > works, which i > > > think but cannot guarantee. > > > > > > cheers > > > luigi > > > > > > > Are you saying that wget bandwidth reading is > > incorrect? I expected to see full speed of the > pipe > > for the first 100KBytes. > > if you see just one line above your patch, > len_scaled is computed as > > int len_scaled = p->bandwidth ? len*8*hz : 0 > ; > > so your '100000' correspond (with HZ=1000) to an > actual burst > of 100 bits or 12.5 bytes so hardly measurable. > secondly, as i said the throughput is limited by > many many factors > even without dummynet (or just because you have > traffic going through > other pipes, etc.). > > finally, i don't know how wget computes times so it > may > be correct or not, i have no idea. since many > programs > do wrong things in computing bandwidths i wouldn't > give for granted that wget is correct in all > situations. > > bye > luigi > > > > I even commented out: > > /* > > if (len_scaled > q->numbytes) > > break ; > > */ > > While I would have expected full throughput, I got > > only ~10X the speed of the pipe: > > > > 0K .......... .......... 0% 8.30 KB/s > > 50K .......... .......... 1% 20.70 KB/s > > 100K .......... .......... 2% 13.80 KB/s > > 150K .......... .......... 3% 13.80 KB/s > > Let me ask my question differently then, do you think it is possible to bypass the pipe restriction (i.e. burst) for say the first 100KBytes ? __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
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