Date: Wed, 1 Oct 2003 11:16:50 -0700 (PDT) From: Nate Lawson <nate@root.org> To: Bruce Evans <bde@zeta.org.au> Cc: current@freebsd.org Subject: Re: umass(4)/uhci(4) REALLY slow Message-ID: <20031001111502.F85421@root.org> In-Reply-To: <20031001142825.K4031@gamplex.bde.org> References: <20030930172903.S82394@root.org> <20031001142825.K4031@gamplex.bde.org>
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On Wed, 1 Oct 2003, Bruce Evans wrote: > On Tue, 30 Sep 2003, Nate Lawson wrote: > > Here are "iostat 5" results for my USB thumb drive on a uhci(4) controller > > with 5.1-CURRENT. On windows on the same box, it runs reasonably quickly. > > On FreeBSD, it really lags. This is for a cp of a large file to a > > msdosfs-mounted flash drive. > > > > da0 > > KB/t tps MB/s > > 1.07 41 0.04 > > 1.00 41 0.04 > > 1.02 41 0.04 > > > > Is there something we're doing on uhci(4) that makes each transfer only > > 1 KB? If we upped it to 32 KB, it would be a more reasonable 1.2 MB/sec > > which is still well under the USB 1.1 max speed. > > This is probably due to something we're not doing in msdosfs. 1K is > probably your msdosfs file system block size. Yes, I checked and it has a 1K block size. The flash device is 64 MB. > msdosfs is missing support > for clustering. None of the lower levels (buffer cache, driver, usb) > in FreeBSD does clustering (the buffer cache has some support for it, > but this is mostly turned off because the file system doesn't ask for > it). The lower levels not in FreeBSD (firmware and hardware) apparently > don't do clustering either. This results in abysmal performance if > the msdosfs block size is small. It would be twice as abysmal with > the minimum block size of 512. Similarly for ffs with small block sizes > and lots of fragments if write clustering is turned off if the drive > doesn't do it. What would need to be done to add msdosfs clustered reads/writes or perhaps do this in a more general way in the buffer cache? -Nate
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