Date: Tue, 8 Oct 2002 13:03:29 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Don Lewis <dl-freebsd@catspoiler.org> Cc: olli@secnetix.de, freebsd-hackers@FreeBSD.ORG Subject: Re: Mount option "nomtime"? Message-ID: <200210082003.g98K3Thx084532@apollo.backplane.com> References: <200210081959.g98JxOvU036374@gw.catspoiler.org>
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:..
:>
:> Another example would be "oops", which is a very fast,
:> lightweight web proxy. It uses cyclic buffer files to
:> store the cached data, similar to INN's CNFS.
:>
:> I think in the above cases, a "nomtime" option would indeed
:> save some unnecessary overhead.
:
:Probably not much, especially if you are using soft updates. The
:in-kernel copy of the inode will get updated on every write, but the
:on-disk copy will only get written when the soft updates timer for it
:goes off, which I think would be once every 10 seconds and is tunable. I
:don't think you'll see much reduction in load compared to all the other
:I/O that's going on.
atime/mtime/ctime updates will collect in the in-memory inode
and only be written to disk when the filesystem sync occurs once
every 30-60 seconds or so. This is how it works with or without
softupdates.
:Noatime won't help much in your examples either. It only buys you a lot
:if the data is spread over a large number of files.
-Matt
Matthew Dillon
<dillon@backplane.com>
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