[saga-rg] proposal for extended file IO

[Andre Merzky]

Quoting [John Shalf] (Jun 14 2005):
> 
> On Jun 14, 2005, at 10:45 AM, Andre Merzky wrote:
> >readv is more posix like, and more generic.  It always works
> >if you are on read level (e.g. HDF5 VFD layer ;-).
> >
> >eread is more powerful: it allows applicatoin specific
> >optimization which is not achievable with readv (the size of
> >the iovecs in the read request is double of the size of the
> >data returned!).
> 
> OK,
> I think we have both arrived at the same overall conclusion.  

Yes, fortunately :-)

> I think 
> eRead would be useful as a way to package an underlying complex service 
> for implementing remote data requests. One must be able to extend the 
> services on both the client and the server side to provide new e-modes 
> to the user that implement these services.  The vector read ops (not 
> necessarily readv/pread, but perhaps something similar that describes 
> patterned reads in a compact form, would be useful for other 
> application use cases where we are are not permitted (or have no 
> desire) touch or extend the remote service.  I think readv/pread is a 
> bit *too* restrictive, but we should have some similarly compact set of 
> read ops that allow for gather/scatter type remote operations that do 
> not require the service be installed on both ends (eg. just client 
> side) in addition to an eRead() interface for access to two-sided 
> services.
> 
> So I guess we have a need to do both.
> 
> For a suitable vread alternative, it would be useful to have something 
> like
> 	read_pattern(descriptor,buffer,int nlogicaldims,int 
> logicaldims[],offset[],block[],stride[]);
> to specify a patterned operation.  The list of iovecs[] can be used for 
> gather operations that cannot be encoded as a regular pattern.

I agree, the other mail.

Cheers, Andre.


> -john



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