NonStop S-Series Server Description Manual (G06.27+)

Interprocessor Communication

HP NonStop S-Series Server Description Manual—520331-004

9-16

Request With Long Request Data

When the combination of request control and data is too big to fit in either the pre-push

buffers or the readlink cache, the message system eliminates use of both of these

elements and instead pulls the data directly to the listener’s buffer. This operation is

shown in Figure 9-8.

In the first part of this phase (upper part of Figure 9-8), only the setup information is

sent from the linker to the listener. This transfer is done as a single-packet message.

For this message, the message system creates a TIB (1), and ServerNet services

translate the TIB to BTE descriptors (2). ServerNet services transfers control to the

BTE (3), which transmits the request setup packet (4) to the AVT hardware in the

listener processor. There, the setup is linked into the interrupt queue (5).

When the interrupt is processed, the message system reads the setup information,

stores it in an MQC in the readlink cache (6), and recognizes that this request contains

request data of long length. Because the message system cannot handle this request

by itself at this level, it goes to the listener and notifies it that it needs to pull the

request data directly to the request data buffer.

In the second part of this phase (middle part of Figure 9-8), the listener successively

calls MSG_READCONTROL_ and MSG_READDATA_ to pull the request control

information and the request data to itself. For each of these calls, the listener’s

message system creates a TIB (7). ServerNet services translates the TIB to BTE

descriptors (8) and transfers control to the BTE (9). The BTE in the listener then

proceeds to issue read request packets to the AVT in the linker processor (10), which,

in corresponding response packets, transmits the original request control information,

followed by the request data (11). The response packets go back to the listener BTE

(12) for storage in the client buffers of the listener process (13).