[mpich-discuss] Limitation of open files on Mira

[jt.meng at siat.ac.cn]

Hi Rob, 
      Can we increase the number of open files on Mira to 1 million?  Currently the number of open files is set to be 65536, and users can increase it manually to its hard limitation of 81920.  
      Can we increase this hard limitation to 1 million for Mira for a one week test on MPI IO in Mira?  Thanks. 

--------------- /etc/security/limits.conf---------------------------------
root            soft    nofile          65536
root            hard    nofile          81920  <--

Best, 


jt.meng at siat.ac.cn
 
From: Latham, Robert J.
Date: 2017-04-19 22:35
To: discuss at mpich.org
Subject: Re: [mpich-discuss] Installation on Blue Gene/Q
On Wed, 2017-04-19 at 13:58 +0200, pramod kumbhar wrote:
> Hi Rob,
> 
> Is this already installed/avaialble on MIRA? I would like to try this
> to check some mpi i/o hints.
 
Yes, there are several versions available:
 
manual progress optimized:
/projects/aurora_app/mpich3-ch4-ofi/install/gnu/bin
 
auto progress optimized:
/projects/aurora_app/mpich3-ch4-ofi/install-auto/gnu/bin
 
manual progress debug:
/projects/aurora_app/mpich3-ch4-ofi/install/gnu.debug/bin
 
auto progress debug:
/projects/aurora_app/mpich3-ch4-ofi/install-auto/gnu.debug/bin
 
There are some performance considerations (both positive and negative)
to consider:
 
Current performance improvements versus [IBM's vendor-supplied MPICH]:
 
1.) Pt2pt latency - better than 2x speedup for small messages, large
ones with few ranks-per-node less so due to detriment #2  listed below.
 
2.) RMA latency - exponentially better for small messages, then becomes
gradually even for large messages in the case of put and get.
 
Current performance detriments versus [IBM's vendor-supplied MPICH]:
 
1.) No optimized collectives -- all collectives are pt2pt algorithms in
MPICH CH4.  There is a plan to develop optimized collectives via OFI
triggered operations but that work wouldn't begin until the April-May
timeframe at the earliest.  There is also a plan to make optimized
pt2pt collectives available sooner.
 
2.) Only 1 rget injection fifo utilized per rank to pt2pt communication
--- pami can utilize up all 11 to maximize internode bandwidth, you
would mainly see this have an impact if you are running < 8 ranks per
node and passing large messages.
 
==rob
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