Date: Fri, 30 Nov 2001 14:20:01 -0800 (PST) From: David Madole <david@madole.net> To: freebsd-bugs@FreeBSD.org Subject: RE: kern/32338: Network to disk write performance low under ATA with DMA Message-ID: <200111302220.fAUMK1264704@freefall.freebsd.org>
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The following reply was made to PR kern/32338; it has been noted by GNATS. From: David Madole <david@madole.net> To: sos@freebsd.dk Cc: freebsd-gnats-submit <freebsd-gnats-submit@FreeBSD.ORG> Subject: RE: kern/32338: Network to disk write performance low under ATA with DMA Date: Thu, 29 Nov 2001 10:27:50 -0500 >===== Original Message From sos@freebsd.dk ===== >It seems David S Madole wrote: >> >Description: >> Data transfers from network to ATA hard drive are very slow. Visible >> with Samba, HTTP PUT, etc., but most easily demonstrated with FTP. >> Only occurs when DMA is enabled on the ATA controller. >> >> Interestingly, only seems to happen when network data is being written >> to the drive. Doing a large write to the drive while simultaneously >> doing a 'ping -f -s 1400' to another node from another session does >> not slow the disk writes significantly. >> >> The drive is a Maxtor 60GB (model number in included dmesg). NIC is >> NetGear with sis driver, although same problem occurs with LinkSys >> card on dc driver. Also occurs with older Maxtor 6GB drive. > >Hmm, this sounds like the SiS network card may be using DMA too >and badly at that, making the net card and the ATA driver >compete for the bus... > >> >Fix: >> I wish I knew where to look! > >Try another netcard, if that helps you know where to look :) I think it's some kind of funniness with the chipset. As I mentioned originally, I get the same problem with a ADMtek AN985 on the dc driver. I also do not get the problem on an Intel Triton-based board with the same NIC and hard drive (and a much slower CPU - P-133 instead of K6-III-550). I added a little bit of instrumentation to the sis driver to keep track of receive descriptor/buffer overflows and it appears to be the problem. If I FTP more than about 150K, I get an overflow and slow performance (from TCP throttling back in response to packet loss). I changed the sis driver code to up the buffers from 128 to 1536, it still overflows. It appears that a NIC interrupt is getting lost, or the interrupt latency is going way up. So what in running the drive under DMA could cause interrupt problems for the NIC? I also forced the drive to WDMA2 instead of UDMA2 to match what the Triton-based machine was doing, but it made no difference. Didn't really expect it would. Dave To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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