[Darshan-users] guidance on using --with-mem-align

[David Shrader]

Hello All,

I am new to Darshan and am working on making it available on our 
clusters. I am having some trouble figuring out what to give the 
--with-mem-align configure parameter. I have read through the 
documentation where I see 8 and 16 used. Is this referring only to the 
minimum read and write size of physical memory on a node (not disk, but 
RAM)? Are there any resources for trying to figure out what this 
parameter should be set to for a particular system? My Google searches 
have come up with some research topics and programs for exposing the 
differences in timing for aligned vs non-aligned writes, but I'm not 
sure how to apply this information to what Darshan is looking for. For 
example, the recipe for IBM Blue Gene/Q sets it to 16 partly because 
"that is the optimal alignment for the network transport used between 
compute nodes and I/O nodes in the system." This statement makes it seem 
like not only is physical memory important, but also network transport.

Does anyone have any resources or guidance on how to think about this 
parameter that they can point me to?

Any and all help is appreciated!
David

-- 
David Shrader
SICORP, Inc
1350 Central Ave
Suite 104
Los Alamos, NM 87544
David.Shrader at SICORP.com

LANL contact information:

LANL #: 505-664-0996
LANL email: dshrader at lanl.gov