Date: Fri, 27 May 2005 08:07:35 -0400 From: Ken Smith <kensmith@cse.Buffalo.EDU> To: Marc Olzheim <marcolz@stack.nl> Cc: freebsd-arch@freebsd.org Subject: Re: Modifying file access time upon exec... Message-ID: <1117195655.88498.9.camel@opus.cse.buffalo.edu> In-Reply-To: <20050527091750.GB91258@stack.nl> References: <1117139065.82793.20.camel@opus.cse.buffalo.edu> <20050527091750.GB91258@stack.nl>
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On Fri, 2005-05-27 at 11:17 +0200, Marc Olzheim wrote:
> On Thu, May 26, 2005 at 04:24:25PM -0400, Ken Smith wrote:
> > Any thoughts before I commit it? The patch itself is pretty small. But
> > given the sections of code it's mucking with combined with it adding a
> > little 'nit' filesystem implementers should be aware of I wanted to run
> > it by as many clueful eyes as possible before doing the final commit.
>
> Has this been run through some kind of real world performance test ? I
> can imagine for instance /bin/sh's vnode is being updated a lot... Would
> it be eligible to a becoming a mount option ?
Bruce did some benchmarking and this approach seemed to be the minimal
hit on performance of the options we have. The other things that got
tested were things like "fake reads". The whole issue started when the
exec mechanisms were shifted away from doing file reads in favor of a
more mmap based mechanism for starting the executables.
>From his tests the hit seemed minimal. The noatime mount option seems
to be the most appropriate thing to use for turning it off, and in that
case the only cost involved with this addition is the check in exec to
see if the file is coming from a filesystem that's either noatime or
readonly.
> I don't see any real problems with it, but perhaps people running
> executables over NFS filesystems that cannot be mounted with noatime
> might have an issue, like netbooting diskless machines...
I'm not sure why you say NFS filesystems can't be mounted with noatime.
--
Ken Smith
- From there to here, from here to | kensmith@cse.buffalo.edu
there, funny things are everywhere. |
- Theodore Geisel |
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