[openib-general] Re: [PATCH] enable the fmr pool user to set the pagesize

[Or Gerlitz]

Michael S. Tsirkin wrote:
> Out of curiosity, why would you want to make the page size smaller than
> PAGE_SIZE?  Bigger pages typically give you better performance, isnt that true
> for iser?

First just for the sake of clarity it is important to emphasize in the 
verbs api level the decoupling of the OS page notation to the "page" 
used by the HCA to map bunch of buffers to one network VA.

Second and indeed more important, from our experience, there are 
eventually IB consumers such as the Linux SCSI Mid-Layer which sometimes 
generate Scatter-Gather lists that are "RDMA aligned" when treated in a 
resolution different from the system PAGE_SHIFT. Example to that we saw 
with ia64 SLES9 SP1/2 kernels. So if you work in PAGE_SHIFT you can not 
produce one VA for many of the SG submitted by the mid-layer.

Or.