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Date:      Tue, 31 May 2005 13:54:51 -0700
From:      Max Okumoto <okumoto@ucsd.edu>
To:        freebsd-arch@freebsd.org
Subject:   Re: Modifying file access time upon exec...
Message-ID:  <429CCF1B.1060702@ucsd.edu>
In-Reply-To: <20050528141302.J81578@delplex.bde.org>
References:  <15835986.1117210354543.JavaMail.root@vms069.mailsrvcs.net>	<1117211600.666.5.camel@opus.cse.buffalo.edu> <20050528141302.J81578@delplex.bde.org>

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Bruce Evans wrote:
[lots of stuff deleted]
> 
> The 10-second granularity might be useful here.  stat() on the other
> client would still need to sync with local caches/marks for update on
> other clients, but the other clients and the server can know that there
> is no need to sync if less than 10 seconds has elapsed since the
> last tick of the 1/10 Hz clock that gives the time to possibly update
> (this clock must be synchronized).
> 
> This wouldn't work for mtimes.  The granularity must be much less than
> 10 seconds for make(1) to work.  I'm surprised it mostly works with a
> granularity of 1 second.
>

I can't confirm this yet, since I have not gotten to that part of
make.  But from the docs, it looks like make(1) caches the stat()
info.  Which might explain why it mostly works over NFS.

make docs in the usr.bin/make/PSD.doc/tutorial.ms Section 4.1

    Something you should know about the  way  search  paths  are
    implemented is that each directory is read, and its contents
    cached, exactly once -- when it is first encountered  --  so
    any  changes  to the directories while PMake is running will
    not be noted when searching for implicit sources,  nor  will
    they  be found when PMake attempts to discover when the file
    was last modified, unless the file was created in  the  cur-
    rent  directory.  While  people  have  suggested  that PMake
    should read the directories each time,  my  experience  sug-
    gests  that the caching seldom causes problems. In addition,
    not caching the directories  slows  things  down  enormously
    because  of  PMake's  attempts to apply transformation rules
    through non-existent files -- the number of extra  file-sys-
    tem  searches  is truly staggering, especially if many files
    without suffixes are used and the null suffix isn't  changed
    from .out.


				Max Okumoto

[stuff deleted]




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