[Openib-windows] RE: CA capabilities

[Yossi Leybovich]

I agree that the access layer should not modify the maximum for each
resource that application takes
But one can say that the same way as the low level driver keep some resource
for its own use and change the maximum values,
same should be with the IBAL, if its need resources for its own use it
should change the maximum.
That because its not client application but the driver to that CA device.
If the CA capable to open x resources but the IBAL take y ,in systems with
memory limits that can be problem.
 
And I agree about other drivers/applications that you can enable/disable
(like IPoIB/SRP) or that not loaded by default.

Yossi 



> -----Original Message-----
> From: Fab Tillier [mailto:ftillier at silverstorm.com]
> Sent: Wednesday, August 10, 2005 7:40 PM
> To: 'Yossi Leybovich'
> Cc: openib-windows at openib.org; Ami Parlmuter
> Subject: RE: CA capabilities
> 
> 
> Please send emails in plain text.
> 
> > From: Yossi Leybovich [mailto:sleybo at mellanox.co.il]
> > Sent: Wednesday, August 10, 2005 4:06 AM
> > 
> > Simple test that try to allocate max PDs (as reported form query ca)
> > discovered that it can allocate only the max_pds -1.
> >
> > I checked it and found that:
> > The user ask for 0x4000 PDs
> > The THH layer keep 2 PDs for itself so the IBAL report on 
> 0x3ffe PDs available
> > while the IBAL is loaded (in creat_ci_ca) IBAL take one 
> more PD (for SQP..) so
> > the user can allocate only 0x3ffd PDs
> > Do you think that IBAL should report 1 PD less so the user 
> will know exactly
> > how many resources he actually can allocate ?
> > Personally I think that if IBAL take resource (PDs, Avs, 
> QPS) for its own use,
> > then it should subtract them from the ca capabilities.
> > What do you think ?
> 
> The maximum number of PDs is what the CA supports.  The 
> access layer, as a
> client, uses a PD.  So does each IPoIB and SRP instance, as 
> well as every
> user-mode process that uses sockets when WSD is enabled.  An 
> application cannot
> rely being able to allocate the maximum reported in the 
> attributes since the CA
> is a shared resource.
> 
> Should the access layer keep modifying the maximum reported 
> to account for
> client usage?  I think not.  The maximum values are there to 
> indicate what the
> hardware is capable of, and is not a guarantee to the 
> application that it will
> be able to allocate all of them.
> 
> - Fab
> 
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