[Pvfs2-developers] disabling ncache

[Robert Latham]

Hey gang

One of the ROMIO tests (noncontig_coll2) started failing around the
time we comitted the revamped ncache.  If I disable the ncache by
setting NCACHE_DEFAULT_TIMEOUT_MSECS to zero, the test passes again.

Sam and I have a couple solutions, but none of them are satsifying
given we need to coordinate any API changes with ROMIO:

- To compliment PVFS2_SET_DEBUGMASK, add a PVFS2_NCACHE_TIMEOUT
  environment variable (this one might be the winner)

- Add a new routine to the pvfs2 API that modifies the ncache timeout
  values.  This would impose a ROMIO pre-req on
  pvfs2-1.whatever-is-next.  

- ignore the problem.  It only shows up if one set of processes
  open/write/read/close a file, it is deleted, and a different set (or
  same set but different order) open/write/read/close the file.  Most
  places that care to set ROMIO's cb_config_list hint aren't going
  to change it when they delete and re-create a file.

I think I'm going to go with the environment variable solution, since
if ROMIO happens to link against an older PVFS2, nothing bad will
happen (as long as they don't go crazy with cb_config_list).   Does
anybody else have any suggestions?

==rob

-- 
Rob Latham
Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
Argonne National Labs, IL USA                B29D F333 664A 4280 315B