Date: Fri, 4 May 2001 09:10:48 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca> Cc: freebsd-stable@FreeBSD.ORG Subject: Re: Mem Use Message-ID: <200105041610.f44GAmr25737@earth.backplane.com> References: <200105040028.f440SoI16925@cwsys.cwsent.com>
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:All this talk of memory utilisation reminds me to ask, are there any
:plans to implement directio (Solaris UFS and VxFS have it)?
There has been talk. It's considered 'interesting' but it is
not a priority. FreeBSD's heuristics already handle write-behind
and free-behind operations so, for example, writing out a 200MB
file sequentially will not blow away your cache.
:Any plans to implement priority paging, e.g. not cache files in memory
:when memory is tight to reduce demand for paging?
The VM system already tunes itself to load. It's not as simple as
deciding whether to cache something or not... *everything* in the
system is part of the cache. It's a matter of balancing demand and
determining when to lunder dirty pages to their backing store. Anything
that isn't dirty is potentially freeable whether it represents
(cached) files, code, data, or anonymous memory. But gratuitously
throwing away file cache pages will kill performance as quickly as
gratuitously throwing away swapped out anonymous memory.
-Matt
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