Date: Thu, 1 Jun 2006 09:18:35 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: "Eugene M. Kim" <freebsd.org@ab.ote.we.lv> Cc: freebsd-hackers@freebsd.org Subject: Re: dump(8) performance Message-ID: <20060531234835.GW54613@wantadilla.lemis.com> In-Reply-To: <447DB0B1.8040206@ab.ote.we.lv> References: <447DB0B1.8040206@ab.ote.we.lv>
next in thread | previous in thread | raw e-mail | index | archive | help
--9Wosya/OiUJZ+2ov Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wednesday, 31 May 2006 at 8:05:21 -0700, Eugene M. Kim wrote: > While watching the output of iostat -dxz -w10 -n100 to monitor the > progress/performance of a dump(8) process straight to a tape, I found > out something interesting and disappointing at the same time: The disk > read throughput was exactly twice as high as the tape write throughput, > throughout the entire dump phases 4 and 5, i.e. dumping actual inodes. > Disappointing, because the tape drive utilization (%busy) was lingering > around 35%-50% for most of the time; I didn't expect the disk would be > the bottleneck. :p > > I want to believe that this indicates a bug in dump(8) which causes each > disk block to be read twice, but being no UFS expert in any sense, I > wonder: Could this behavior be by design, and would there be any room > for improvement? Without looking at the code, this seems unlikely. But you might get more information by attaching a ktrace to the dump process for a short period of time (find the pid, then ktrace -p<pid> to start trace, ktrace -p<pid> -C to stop again). If you do that, let me see no more than 30 lines of repetitive trace. Greg -- See complete headers for address and phone numbers. --9Wosya/OiUJZ+2ov Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (FreeBSD) iD8DBQFEfitTIubykFB6QiMRAnhAAKCMKBfWpWMhn4wrYSGz6aEK+VcU5gCfQSiY FPDtd80GvrsdOtfkwunSvn0= =r0mD -----END PGP SIGNATURE----- --9Wosya/OiUJZ+2ov--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20060531234835.GW54613>