[ofa-general] How much pinned memory each QP needs ?

[Roland Dreier]

 >         We are running a big system with some memory issue(16K QPs), I want to know how much
 > pinned memory each QP needs, the settings when creating QP is follows:
 > 
 >         qp_init_attr.cap.max_send_wr = 136;
 >         qp_init_attr.cap.max_recv_wr = 1;
 >         qp_init_attr.cap.max_send_sge = 1;
 >         qp_init_attr.cap.max_recv_sge = 1;
 >         qp_init_attr.cap.max_inline_data = 128;

Not sure really without tracing through the code.  The easiest way to
find out would probably be to add a print statement into the low-level
driver library to find out how big a buffer it allocates for the QP.

Naively, the max_send_wr is going to be rounded up to a power of 2, so
256, and so will the work request size, which has to be over the
inline data size of 128, so that will be 256 bytes.  So I would guess
you'll end up using about 256 * 256 or 64 KB per QP.

 - R.