Use these steps to estimate the minimum real memory requirements
for Shared Memory Communications over RDMA (SMC-R).
Procedure
Perform the following steps:
- Determine the number of IBM® 10GbE
RoCE Express® interfaces
to be activated.
- For each TCP/IP stack, determine the number of expected
SMC-R link groups. You can determine the number of link
groups by the number of VLANs that are supported, and the number of
peer hosts per VLAN. For instance, if two VLANs are defined (VLAN1
and VLAN2), two peers are expected to connect to VLAN1, and four peers
are expected to connect to VLAN2, then the number of expected SMC-R
link groups is six.
- Use these values to complete Table 1 for
each TCP/IP stack, where PFIDs is the number of
10GbE RoCE Express interfaces
and connections is the number of SMC-R link groups.
Table 1. Worksheet 1, minimum TCP/IP stack
memory estimates| Resource Description |
Your Environment |
Total Memory |
Notes |
|---|
| Number of PFIDs |
PFIDs * 1 MB |
x MB |
RDMA receive element buffers |
| Staging buffers and transmit elements |
|
5 MB |
Initial allocation of staging buffers and RDMA
transmit elements |
| Peer connections |
connections * 3 MB |
y MB |
Initial RMB allocations per SMC-R link groups |
| TCP workloads |
|
0 MB |
TCP/IP variable SMC-R storage allocations |
| Total initial TCP/IP stack requirements |
|
total MB |
Sum of rows 1, 2, and 3 |
- Sum the totals of the Total Memory column that are calculated
for each stack in Table 1,
and enter the overall total into the second row of Table 2.
- Complete Table 2,
which provides the minimum amount of fixed storage that is required
to use SMC-R communications.
Table 2. Worksheet
2, minimum z/OS Communications
Server memory estimates| Resource Description |
Your Environment |
Total Memory |
Notes |
|---|
| Number of PFIDs |
PFIDs * 8 MB |
x MB |
10GbE RoCE Express Data
Link Control (DLC) memory that is managed by VTAM® |
| Sum of TCP/IP stack requirements |
|
y MB |
Sum of the values that are calculated for each
stack by using Table 1 |
| Total initial z/OS® Communications
Server requirements |
|
total MB |
Sum of rows 1 and 2 |
Example for calculating
SMC-R storage requirements
Assume an installation with the
following characteristics:
- Two TCP/IP stacks, both SMC-R capable
- Two 10GbE RoCE Express ports,
each shared by the two TCP/IP stacks
- Stack A is not using VLANs, and expects to connect to four peers
- Stack B is using VLANs, with the following connectivity expectations:
- VLAN-1 connects to two peers
- VLAN-2 connects to four peers
- Initially a small number (16) of TCP connections use SMC-R, all
with the same RCVBFRSIZE value of 32 KB. On average, this number of
TCP connections does not require allocation of any additional RMBs.
For more information, see TCP/IP variable SMC-R storage allocations.
Using the values for stack A provides the worksheet 1 results
that are shown in Table 3.
Table 3. Stack A, worksheet 1| Resource Description |
Your Environment |
Total Memory |
Notes |
|---|
| Number of PFIDs |
2 * 1 MB |
2 MB |
RDMA receive element buffers |
| Staging buffers and transmit elements |
|
5 MB |
Initial allocation of staging buffers and RDMA
transmit elements |
| Host connections |
4 * 3 MB |
12 MB |
Initial RMB allocations per SMC-R link groups |
| TCP workloads |
|
0 MB |
TCP/IP variable SMC-R storage allocations |
| Total initial TCP/IP stack requirements |
|
19 MB |
Sum of rows 1, 2, and 3 |
Using the values for stack B provides the worksheet 1 results
that are shown in Table 4.
Table 4. Stack B, worksheet 1| Resource Description |
Your Environment |
Total Memory |
Notes |
|---|
| Number of PFIDs |
2 * 1 MB |
2 MB |
RDMA receive element buffers |
| Staging buffers and transmit elements |
|
5 MB |
Initial allocation of staging buffers and RDMA
transmit elements |
| Host connections |
6 * 3 MB |
18 MB |
Initial RMB allocations per SMC-R link groups |
| TCP workloads |
|
0 MB |
TCP/IP variable SMC-R storage allocations |
| Total initial TCP/IP stack requirements |
|
25 MB |
Sum of rows 1, 2, and 3 |
Using the values from Table 3 and Table 4 provides
the worksheet 2 results that are shown in Table 5.
Table 5. Worksheet 2 minimum memory estimates
for sample network| Resource Description |
Your Environment |
Total Memory |
Notes |
|---|
| Number of PFIDs |
2 * 8 MB |
16 MB |
10GbE RoCE Express DLC
memory managed by VTAM |
| Sum of TCP/IP stack requirements |
|
44 MB |
Sum of the values that are calculated for each
stack in Table 3 and Table 4 |
| Total initial z/OS Communications
Server requirements |
|
60 MB |
Sum of rows 1 and 2 |