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From Paul Richards <>
Subject Re: HP-UX and BSDI mmap()
Date Thu, 10 Aug 1995 10:08:31 GMT
In reply to David J. Hughes who said
> On the next SELECT or UPDATE, the table region is unmapped and then 
> mapped again to ensure the new rows are available to the engine.  This 
> works fine on most boxes (SunOS, Solaris, OSF1, FreeBSD, NetBSD, Linux 
> 1.3.x etc) but fails on HP-UX and BSDI 2.x (worked on BSDI 1.x).  It 
> appears that if you use write() to update a file while it is mapped, 
> HP-UX and BSDI get very confused, the result being that the newly written 
> data is trashed in a random way.

I'd bet that is a cache coherency problem and the only OS I'd trust
would be FreeBSD since we have a merged vm/buffer cache and coherency
is something we've explicitly fixed.

  Paul Richards, Bluebird Computer Systems. FreeBSD core team member. 
  Phone: 0370 462071 (Mobile), +44 1222 457651 (home)

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