Eric Schrock wrote:
On Thu, Jul 06, 2006 at 09:53:32PM +0530, Pramod Batni wrote:
offtopic query :
How can ZFS require more VM address space but not more VM ?
The real problem is VA fragmentation, not consumption. Over time, ZFS's
heavy use of the VM system causes the address space to become
fragmented. Eventually, we will need to grab a 128k block of contiguous
VA, but can't find a contiguous region, despite having plenty of memory
(physical or virtual).
Interesting, I saw and helped debug a very similar sounding problem
with VxVM and VxFS on an E10k with 15TB of EMC storage and 10,000 NFS
shares years ago. This was on Solaris 2.6 so even though it was
UltraSPARC CPU there was still only a 32bit address space.
Jeff Bonwick supplied the fixes for this, I don't remember the details
but it did help reduce the memory fragmentation. It does make me
wonder though if these fixes that were applicable to 32bit SPARC work
for 32bit x86.
--
Darren J Moffat
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