Ming Zhang wrote:
On Tue, 2005-03-01 at 13:37, Arjan van de Ven wrote:
On Tue, 2005-03-01 at 10:24 -0800, Bryan Henderson wrote:
One thing that's implicit in your reasons for wanting to be in the kernel
is that you've chosen to exploit the kernel's page cache. As a user of
the page cache, you have more control from inside the kernel than from
user space. The page cache was designed to be fundamentally invisible to
user space.
A pure user space implementation of an ISCSI target would use process
virtual memory for a cache and manage it itself. It would access the
storage with direct I/O.
why would it use direct I/O ? Direct I/O would be really stupid for such
a thing to use since that means there's no caching going on *at all*.
what Bryan suggest is a privately owned and managed user space cache. so
for that disk write should be real write-through.
it is hard to beat linux kernel cache performance though.
A privately managed user space cache uses Linux kernel cache.
As does mmap/sendfile...
Jeff
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