Bob Friesenhahn wrote:
On Sat, 4 Jul 2009, Phil Harman wrote:
However, this is only part of the problem. The fundamental issue is
that ZFS has its own ARC apart from the Solaris page cache, so
whenever mmap() is used, all I/O to that file has to make sure that
the two caches are in sync. Hence, a read(2) on a file which has
sometime been mapped, will be impacted, even if the file is nolonger
mapped.
However, it seems that memory mapping is not responsible for the
problem I am seeing here. Memory mapping may make the problem seem
worse, but it is clearly not the cause.
mmap(2) is what brings ZFS files into the page cache. I think you've
shown us that once you've copied files with cp(1) - which does use
mmap(2) - that anything that uses read(2) on the same files is impacted.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us,
http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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