[ofw] "ibv_poll_cq" function in verbs.cpp

[Leonid Keller]

agree 

> -----Original Message-----
> From: ofw-bounces at lists.openfabrics.org 
> [mailto:ofw-bounces at lists.openfabrics.org] On Behalf Of Sean Hefty
> Sent: Friday, August 07, 2009 7:43 PM
> To: 'Sivaselvam Narayanasamy'; ofw at lists.openfabrics.org
> Subject: RE: [ofw] "ibv_poll_cq" function in verbs.cpp 
> 
> >Is there any performance overhead in user mode cq polling ( 
> ibv_poll_cq  
> >function ) compared to doing the polling from kernel mode?
> 
> Someone from Mellanox would need to confirm this, but I don't 
> believe so.
> 
> The user space call basically goes directly to the provider 
> library.  If you compare the user space code with the kernel 
> code (e.g. mthca_cq.c:mthca_poll_one versus 
> mlnx_uvp_cq.c:mthca_poll_one), they look identical.  And I 
> don't think there's any difference writing the CQ entries for 
> a CQ that was allocated for a user space client versus a 
> kernel client.
> 
> - Sean
> 
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