Date: Sun, 08 Jan 2012 22:21:50 +0000 From: Poul-Henning Kamp <phk@phk.freebsd.dk> To: current@freebsd.org Subject: CD9660/md(4)/UFS22 silly behaviour Message-ID: <8334.1326061310@critter.freebsd.dk>
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I'm doing som data-mining on a pile of ISO images right now.
I stuck the ISOs on a UFS2 on a flash-disk for speed, and mdconfig(8)'d
them so I could mount them.
The traffic pattern his "interesting":
dT: 1.003s w: 1.000s
L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name
[...]
1 733 733 1466 1.3 0 0 0.0 98.2| md39
1 733 733 23449 1.3 0 0 0.0 93.2| da0
Notice the 1:16 ratio on kBps but 1:1 ratio on ops/s ?
da0's UFS2 has 32k block-size:
magic 19540119 (UFS2) time Wed Jan 4 16:41:47 2012
superblock location 65536 id [ 4f046cf5 c30697ee ]
ncg 104 size 19537685 blocks 19228156
bsize 32768 shift 15 mask 0xffff8000
fsize 4096 shift 12 mask 0xfffff000
[...]
It looks like every 2k read from CD9660 turns into a 32k block
read in the UFS filesystem, without any beneficial caching happening.
Less than optimal I'd say...
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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