[MITgcm-devel] local (tiled) MDSIO

[Martin Losch]

Hi Jean-Michel,

here's what I find for verification/deep_anelastic (no modifications  
of data files, 4 tiles)
on 2009-05-31 04:20 (so before you changes)
PID.TID 0000.0001)   Seconds in section "ALL                     
[THE_MODEL_MAIN]":
(PID.TID 0000.0001)           User time:  13.26000034343451
(PID.TID 0000.0001)         System time:  1.430000022053719
(PID.TID 0000.0001)     Wall clock time:  15.95677185058594
today (after your changes):
(PID.TID 0000.0001)   Seconds in section "ALL                     
[THE_MODEL_MAIN]":
(PID.TID 0000.0001)           User time:  12.71000026725233
(PID.TID 0000.0001)         System time:  1.395000047981739
(PID.TID 0000.0001)     Wall clock time:  15.20528006553650

So faster, but not significantly. The reason is probably, that for the  
GSFS of the SX8 the batches of IO are still very small. The system  
considers basically everything below 1GB as small (o:

Martin



On Jun 1, 2009, at 4:34 PM, Jean-Michel Campin wrote:

> Hi Martin,
>
> I've check-in a modification to MDSIO pkg such as tiled IO are
> now done by chunk of 1-level tile (instead of 1-line of length sNx).
> I remember you reported that non-SingleCpuIO was slower than
> SingleCpuIO because of many small read/write pieces.
> This modification should improve the speed of those IO,
> and it would be interesting to see if it really does (because it's
> still a matter of platform/disk system ...).
>
> I've did some short test with lot of IO, and in the most favorable one
> (verification/deep_anelastic), without any Optimisation, I get:
> std_outp.new   User: 13.3799661 System: 0.490924996 Wall clock:  
> 14.110111
> std_outp.ref   User: 15.7935989 System: 6.53900592 Wall clock:  
> 22.7398989
> In other cases, I've seen also a reduction of the System time,
> but the wall-clock time improvement was not as big.
>
> Cheers,
> Jean-Michel
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