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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.freebsd.misc,comp.os.linux.development.system
Subject: Re: The better (more suitable)Unix?? FreeBSD or Linux
Date: 22 Feb 1996 00:10:28 GMT
Organization: Utah Valley State College, Orem, Utah
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Message-ID: <4ggc9k$kbv@park.uvsc.edu>
References: <4ftjt9$fjs@park.uvsc.edu> <DMv8w7.8H4@pe1chl.ampr.org> <4g5ivp$28m@park.uvsc.edu> <4ge2qa$2gm@park.uvsc.edu>
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mday@park.uvsc.edu (Matt Day) wrote:
]
] In article <4g5ivp$28m@park.uvsc.edu> Terry Lambert <terry@lambert.org> writes:
] >4) Sync makes no difference in user perception of speed
] > unless you're the type of user who lives to run bogus
] > benchmarks, and then claim they represent a single
] > figure-of-merit to use when picking your machine.
]
] I disagree. ``rm -r'' runs much more slowly on a file system that does
] synchronous metadata updates, and that's just for starters. In many
] cases worth caring about, synchronous metadata updates have a
] significant negative impact on "user perception of speed". Do you
] honestly think Ganger and Patt did all that soft updates research just
] to optimize for bogus benchmarks?
The vast majority of file usage in an installed end user site
is manipulation of existing files.
Mass file deletion is infrequent.
I think the soft updates research was done to address file system
performance problems (yes, metadata updates are specifically
mentioned in the abstract, and yes, mass deletes are one example
of this -- but not the only example).
Soft updates increase overall concurrency, more than could be
achieved with delayed writes. The address the order dependency
as a graph problem, though the soloution is not nearly as general
s I'd like.
Soft updates are a sigificant, geeral win, and they happen to
address many issues, of which the lmbench create/delete performance
is one.
This does not validate the lmbench create/delete test as being a
correct benchmark.
The "rm" overhead is a result of POSIX semantic requirements; as
you yourself have pointed out, these requirements can be, in some
cases, more favorably interpreted than UFS chooses to interpret
them.
I believe your perception test to be atypical of common usage;
can you claim the FS operations you are performing to be typical,
or do they fall more into the category of "stress testing"?
Terry Lambert
terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.