STREAMS/UX for the HP 9000 Reference Manual

STREAMS/UX Multiprocessor Support

Writing MP Scalable Modules and Drivers

different queue pairs run in parallel. (A queue pair is also known as a

module instance.) For example, assume that the echo driver in Figure 1 is

conﬁgured for queue pair synchronization. STREAMS/UX runs ECHO-A's

echo_rput, echo_rsrv, echo_wput, and echo_wsrv one at a time. In other

words, STREAMS/UX does not execute any of ECHO-A's echo driver

functions concurrently, nor will STREAMS/UX run any of ECHO-B's echo

driver functions in parallel. However, STREAMS/UX can run an ECHO-A

function at the same time as an ECHO-B function. Also, any of ECHO-A's

functions can run in parallel with DLPI-A or SAD-A routines. If a module

uses queue pair synchronization, a queue pair's functions run one at a time

and can share data.

The module synchronization level serializes access to all of a module's

queue pairs or instances. STREAMS/UX runs only one function at a time for

all of a module's queue pairs. However, STREAMS/UX runs functions for

different modules in parallel. Modules are different if they have different

master ﬁle entries. For example, timod and tirdwr are different modules.

Assume that the echo driver in Figure 1 is conﬁgured for module

synchronization. STREAMS/UX does not run echo driver functions in

ECHO-A and ECHO-B in parallel.

However, STREAMS/UX can run an echo driver function at the same time

as dlpi or a sad driver function. Because STREAMS/UX allows only one

function for all of a module's queue pairs to run at a time, the module's queue

pairs can share data.

The elsewhere synchronization level serializes a group of different modules.

STREAMS/UX runs only one function at a time for the group of modules.

STREAMS/UX runs functions in different groups concurrently. Suppose the

echo and dlpi drivers in Figure 1 are conﬁgured to be members of an

elsewhere synchronization group. Also, assume the sad driver is conﬁgured

to be in a different elsewhere group. Only one driver function in ECHO-A,

ECHO-B and DLPI-A can run at a time. However, a function in ECHO-A,

ECHO-B or DLPI-A can run in parallel with a function in SAD-A. Also, a

function in ECHO-A, ECHO-B or DLPI-A can run at the same time as a

function in a module which uses a different synchronization level than

elsewhere. The modules in a group can share data.

The global synchronization level does not provide parallelism within

STREAMS/UX. Only one module out of those conﬁgured for global

synchronization can run at a time. Suppose that in Figure 1, the echo, dlpi