JPH056219B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] Queue anchor (control table) for input/output requests
In this system, a control flag is provided for each of the plurality of channel processing devices, and the channel processing device that determines that it cannot service the queue turns on its own control flag and stops further service. be.

[Industrial application field]

The present invention relates to a channel path control method in a computer system, particularly a large computer system in which a channel processing unit provided separately from a central processing unit selects a channel bus to be activated. .

[Conventional technology]

A physical/logical communication path used for data transfer and control of individual input/output devices is called a channel path. Currently, the mainstream technology is to offload the state management or control of these paths to a channel processing device that exists independently from the central processing device. In this regard, in order to process input/output requests issued by the central processing unit, a queue with a structure that matches the input/output configuration and the channel path is provided, and the channel processing unit actively fetches and dequeues the queue. A technology has been developed in which input/output processing is started by These queues are provided for each group of channel paths connecting main memory and input/output devices.
Therefore, a certain queue entry cannot necessarily be processed by all of the plurality of channel processing devices. Also, some of the queue entries may relate to input/output devices that are connected to only one path of the path group to which the queue belongs. In this case, only the channel processing device that has that path can execute processing related to this entry.

[Problem to be solved]

However, the channel processing device cannot recognize that the entry is something it cannot process until it actually fetches the entry. Moreover, when fetching an entry for a certain queue, this queue must be exclusively monopolized, which interferes with the operation of other channel processing devices that can service this queue, resulting in overhead. is large.

The present invention was created with this in mind, and it is an object of the present invention to reduce as much as possible the overhead caused by exclusive access of queues by channel processing devices.

[Means for solving problems]

Therefore, in the channel path control method of the present invention, input/output requests issued by the central processing units 1 and 2 are
It is managed by a queue whose entry is the control information storage unit 18,..., 21 that controls the input/output device that is the target of the input/output request, and a plurality of channel processing devices 5, 6 are assigned to each queue. In a computer system in which input/output processing is started by active access, control flags 22 and 23 corresponding to each channel processing device 5 and 6 are provided in the anchors 16 and 17 of each queue, and each channel processing device (a) Exclusively excludes the top entries 18 and 20 of the queue on the condition that one of the control flags 22 and 23 provided in the anchors 16 and 17 of the queue is off; If the entry 18, 20 cannot be processed by itself and can be processed by another channel processing device after the queue has been monopolized, when the queue is released, the anchor 16 of the queue is , 17, the control flag corresponding to itself is set on, and (b) when attempting to exclusively monopolize the top entries 18, 20 of the queue, first A plurality of control flags 22 and 23 provided on the anchor of the cue
, and if the corresponding control flag is on, do not perform exclusive monopolization and stop service to the queue; (c) When dequeuing the queue entry,
This feature is characterized in that it is configured to reset all control flags 22 and 23 provided on the anchor of the cue.

〔Example〕

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention. In FIG. 1, 1 and 2 are central processing units, 3
is a storage control unit, 4 is a main memory, 5 and 6 are channel processing units, 7 to 10 are channels, 12 to 14 are channel paths, 16 and 17 are control tables, 18 to 21 are subchannels, 31 to 34 are inputs. Each output device is shown. In the input/output configuration shown in FIG.
There are two path groups: a first path group to which input/output devices 33 to 32 belong and channel paths 12 to 14 are included, and a second path group to which input/output devices 33 to 34 belong and only channel path 15 is included. Subchannels that correspond one-to-one to each input/output device and reflect the respective states are placed in a hardware area on the main memory. The subchannel uses the CCW address, the area that holds the unit status and channel status when interrupting the central processing unit, the type of input/output device and other control information, and which path given by the central processing unit. It has information that tells it to do so, information that shows the logical interrupt level at the time of an interrupt, and so on. In the illustrated example, it is assumed that queue entries are these subchannels, and these queues are configured for each of the above path groups, and queue management is performed using control tables 16 and 17 provided corresponding to the path groups. Suppose that it is done by.

18 subchannels corresponding to each input/output device
If there is an input/output request waiting to be processed in all of 21 to 21, their connection relationship will be as shown in FIG. Note that when the central processing unit issues an input/output command, firmware on the central processing unit side or the channel processing unit side generates a subchannel and connects this to the corresponding queue. All subchannels form a queue by indicating the next subchannel with a one-way pointer. An invalid value is written in the next pointer of the subchannel, which is the bottom entry of the queue. In addition, the path group control table 1
6 and 17 also point to each other with bidirectional pointers.
Now, the channel processing device 5 exclusively monopolizes the second path group, that is, the control table 17,
Assume that a service of subchannel 20, which is the top entry, is attempted. This attempt, of course, fails. This is because the input/output device 33 corresponding to the subchannel 20 has a channel path only to the channel processing device 6. The subchannel 20 includes information indicating that the channel processing device 5 cannot access the input/output device 33 corresponding to the subchannel 20. If the present invention is not adopted, this channel processing device 5
During the exclusive monopolization of the second path group by the channel processing device 6, the channel processing device 6 tries to access this queue, and if the access fails, the channel processing device 6 moves to the next path group. , a situation may arise in which no service is provided to the second path group. If the present invention were adopted, the channel processing device 5 would select the channel processing device 5 of the control bits 22 and 23 in the control table 17 when the exclusive monopoly is released for the first time.
Turn on bit 22 corresponding to . Next, when the channel processing device 5 attempts to monopolize the control table 17 again, the channel processing device 5
recognize that it is on, and do not have an exclusive monopoly. This ensures that service by the channel processing device 6 to the second bus group is not interrupted. When channel processor 6 begins servicing second path group 2 and thereby dequeues subchannel 20, channel processor 6 dequeues bit 22.
and 23. The top entry from the queue may be dequeued immediately when it is determined that it can be processed, or it may be dequeued after input/output processing is completed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the overhead caused by exclusive access to a queue by a channel processing device that cannot process the data can be significantly reduced compared to the conventional method. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention, and FIG.
The figure is a diagram showing an example of the configuration of a queue in the present invention. 1 and 2...Central processing unit, 3...Storage control unit, 4
...Main memory, 5 and 6...Channel processing unit, 7 to 10...Channels, 12 to 14...Channel paths, 16 and 17...Control tables, 18 to 21
...Subchannel, 31 to 34...I/O device.

Claims (1)

[Claims] 1. An input/output request issued by the central processing units 1, 2 is sent to a queue whose entry is the control information storage unit 18, ..., 21 that controls the input/output device that is the target of the input/output request. In a computer system in which a plurality of channel processing devices 5, 6 actively access each queue to start an input/output device, the anchors 16, 17 of each queue are Control flags 22 and 23 corresponding to the channel processing devices 5 and 6 are provided, and each channel processing device 5 and 6 selects its own control flag among the control flags 22 and 23 provided in the anchors 16 and 17 of the QU. After exclusively monopolizing the top entries 18 and 20 of the queue on the condition that the queue is off, if the entries 18 and 20 cannot be processed by the queue and cannot be processed by another channel processing device, If possible, when releasing the cue, one of the plurality of control flags 22 and 23 provided on the anchors 16 and 17 of the cue is set to ON, and (b) the cue is released. When attempting to exclusively monopolize the top entries 18 and 20 of the queue, first, a plurality of control flags 22 and 23 provided in the anchors of the queue are set.
, and if the corresponding control flag is on, do not perform exclusive monopolization and stop service to the queue; (c) When dequeuing the queue entry,
It is configured to reset all control flags 22 and 23 provided on the anchor of the cue. A channel path control method characterized by: