Date: Sun, 04 Sep 2005 00:38:03 +0200 From: Benjamin Lutz <benlutz@datacomm.ch> To: FreeBSD-Current <current@freebsd.org> Subject: Very slow disk writes because of wdrain Message-ID: <431A25CB.8050503@datacomm.ch>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF87B48B842847D74CC9623D1 Content-Type: multipart/mixed; boundary="------------070801050104030503010500" This is a multi-part message in MIME format. --------------070801050104030503010500 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hello, I've upgraded a Server of mine to FreeBSD-6.0-BETA3 today (fresh install), and I've run into a problem. Writes to the disk are extremely slow, eg: $ dd if=/dev/zero of=/usr/test bs=1048576 count=100 100+0 records in 100+0 records out 104857600 bytes transferred in 13.771165 secs (7614287 bytes/sec) $ During the write, dd spends pretty much all it's time in the wdrain state, CPU usage is about 5% (this is a Pentium 4 2.4GHz). Reading from the disk (as far as I can tell by dd'ing stuff to /dev/null) is as fast as it's supposed to be. wdrain is defined in /usr/src/sys/kern/vfs_bio.c:384. A posting to questions in march last year recommends increasing vfs.hirunningspace (default: 1M) to 4M. This has no impact however on the speed, nor does increasing it to 16M. The disk in question is a SCSI RAID 1 array, which has been working very well under FreeBSD 4.11 before. I'm running a custom kernel with the debugging options as well as the hardware I don't use removed. Please see the attached dmesg.txt and kernel.txt for details. Now, I'd like to get fast speeds again from this machine, can anyone help me? Thanks, Benjamin --------------070801050104030503010500-- --------------enigF87B48B842847D74CC9623D1 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (Darwin) iD8DBQFDGiXRgShs4qbRdeQRAsJbAJ9sAojdcTEaN/sL4RwFiGYX0t4vPwCggZnp Ged9TKv4L68XYb4M2gGoK3c= =Cpir -----END PGP SIGNATURE----- --------------enigF87B48B842847D74CC9623D1--
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