[MPICH] slow IOR when using fileview

[Robert Latham]

On Mon, Jul 02, 2007 at 03:41:56PM -0500, Wei-keng Liao wrote:
> Can you let me know where in ROMIO this fcntl() is called? I wonder why it 
> is called when I used a fileview and not when fileview is not used.

Hi Wei-keng and others:

ROMIO calls fcntl to claim/release locks in the routine
ADIOI_Set_lock.  ADIOI_Set_lock is the main function for
the ADIOI_WRITE_LOCK, ADIOI_READ_LOCK, and ADIOI_UNLOCK macros.

Why are these lock/unlock calls being made when you use a fileview?
As Rajeev said yesterday, you are passing in a type that is
logically contiguous, but has a type signature such that ROMIO treats
it as a noncontiguous type.   

When you don't use a file type, ROMIO treats the operation as
contiuous and makes no fcntl calls.

If you make ROMIO use ADIOI_GEN_ReadStrided_naive somehow, would that
get better performance?  Looks like you can get that by disabling data
sieving.  

Rajeev already suggested increasing cb_buffer_size.  What if you also
increased ind_wr_buffer_size and ind_rd_buffer_size?  

==rob

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