JP2012195766A - Packet transmission control apparatus and packet transmission control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packet transmission control apparatus and packet transmission control method capable of effectively restricting the delay of high-priority packets and/or deterioration of throughput when processing of a communication protocol is mainly realized by software such as in a mobile communication terminal.SOLUTION: A packet transmission control apparatus 1 according to the present invention includes: an interface queue 20L for storing a low-priority packet PL; and an interface queue 20H for storing a high-priority packet PH. A transmission queue 30 can store packets PL output from the interface queue 20L and packets PH output from the interface queue 20H. The packet transmission control apparatus also includes: a hardware interrupt handler 35 for handling hardware interrupts from a communication controller 40; and a software interrupt scheduler 100 for starting a software interrupt handler 25 corresponding to the interface queue to be called by a task scheduler 150, which is responsible for task switching.

Description

  The present invention relates to a packet transmission control apparatus and a packet transmission control method for controlling the transmission order of packets generated by an application on a mobile communication terminal according to priority.

  In personal computers (PCs), communication is often performed simultaneously by a plurality of applications such as online games, content upload / download, program updates, and P2P. In recent years, with the increase in functionality of mobile communication terminals, a situation in which a plurality of applications communicate at the same time, such as a mail incoming inquiry being performed while browsing the web, is increasing.

  However, since the mobile communication terminal has a small transmission capacity, if communication is performed in the background, the throughput is reduced, and communication such as web page browsing performed in the foreground is greatly delayed. Therefore, in order to prevent the user operability from being affected even when a plurality of applications communicate simultaneously, priority control of packets in the mobile communication terminal is required.

  Although packet priority control is implemented by hardware in dedicated communication terminals such as routers, packet protocol control is also implemented in mobile communication terminals used for various purposes because the communication protocol stack is configured by software. Must be implemented in software. Since the software realizes the desired operation by sequential processing by the CPU, if the processing execution order does not match the packet priority, the priority inversion of the packet occurs and a delay occurs in high priority communication (for example, Non-Patent Document 1).

H. Tokuda et al., "Priority Inversions in Real-Time Communication", IEEE RTSS, 1989

  As described above, if communication is simultaneously performed by a plurality of applications on a mobile communication terminal, communication delays in the foreground and throughput are deteriorated. The low priority packet is first sent from the transmission queue of the mobile communication terminal onto the communication path, and the high priority packet stays on the communication path without being sent until the transmission of the low priority packet is completed. Because.

  Therefore, the present invention has been made in view of such a situation, and in the case where most processing related to communication, such as a mobile communication terminal, is realized by software, the effect of delay of high priority packets and deterioration of throughput are effective. It is an object of the present invention to provide a packet transmission control apparatus and a packet transmission control method that can be suppressed.

  The first feature of the present invention includes an interface queue (interface queue 20) prepared for each network interface and a transmission queue (transmission queue 30) included in the device, and application tasks (application tasks 10H, 10M, and 10L). ) Generated based on the low priority packet (for example, packet PL) and the high priority packet (for example, packet PH) generated based on the application task and having a higher priority than the low priority packet to be transmitted Packet transmission control device (packet transmission control device 1) for controlling the transmission order of the first interface queue (for example, interface queue 20L) storing the low priority packet, and the high priority Packets are stored in the first interface queue from the first interface queue. At least a second interface queue (for example, an interface queue 20H), and the transmission queue includes the low priority packet output from the first interface queue and the high priority output from the second interface queue. Packets can be stored and called from a hardware interrupt handler (hardware interrupt handler 35) or a task scheduler (task scheduler 150) that processes hardware interrupts from hardware (communication controller 40), A software interrupt scheduler (software interrupt scheduler 100) for activating a software interrupt handler (software interrupt handler 25); When activated from a hardware interrupt handler or a task scheduler that switches tasks, it is determined whether to activate a software interrupt handler for the first interface queue or the second interface queue based on the priority. This is the gist.

  In the first aspect of the present invention, the software interrupt scheduler includes the priority, the storage status of the low priority packet in the first interface queue, and the storage of the high priority packet in the second interface queue. Based on the situation, it is determined whether to activate a software interrupt handler for the first interface queue or the second interface queue, and the second interface queue is a software interrupt for the second interface queue by the software interrupt scheduler. The high-priority packet is output to the transmission queue, and the first interface queue is software interrupted to the first interface queue by the software interrupt scheduler. Based on, it is preferable to output the low-priority packet to the transmission queue.

  In the first aspect of the present invention, the software interrupt scheduler stores priorities of the low priority packet and the high priority packet generated based on the application task, and is based on the stored priority. It is preferable to determine the software interrupt handler to be activated.

  In the first aspect of the present invention, the capacity of the transmission queue is determined so that the hardware is on a communication path before the low priority packet or the high priority packet is stored in the transmission queue from the interface queue. It is preferable that the data size can be reduced to a maximum size.

  The second feature of the present invention is that the interface queue prepared for each network interface and the transmission queue of the device are generated based on the low priority packet generated based on the application task and the application task. A packet transmission control method for controlling a transmission order of high-priority packets having a higher priority than the low-priority packets, wherein the interface queue stores the low-priority packets. And a second interface queue for storing the high priority packet, wherein the transmission queue is the low priority packet output from the first interface queue, and the second interface queue is output from the second interface queue. Storing high priority packets Activating a software interrupt handler for the interface queue based on a call from a hardware interrupt handler that processes hardware interrupts from hardware or a task scheduler that performs task switching, and the software interrupt handler In the step of activating the software interrupt handler handler for the first interface queue or the second interface queue based on the priority when the hardware interrupt handler or the task scheduler is activated. The gist is to determine.

  According to the features of the present invention, a packet transmission control device capable of effectively suppressing delay of a high priority packet and deterioration of throughput in the case where most processing related to a communication protocol is realized by software, such as a mobile communication terminal, and A packet transmission control method can be provided.

FIG. 2 is a functional block configuration diagram of a packet transmission control device 1 according to an embodiment of the present invention. FIG. 5 is a diagram showing a control operation flow of a packet transmission order by the packet transmission control device 1 according to the embodiment of the present invention. FIG. 11 is a diagram showing an operation concept of application tasks 10H, 10M, and 10L when there is free space in the transmission queue 30 according to the embodiment of the present invention. FIG. 6 is a diagram showing an operation concept of the software interrupt scheduler 100 when there is no free capacity in the transmission queue 30 according to the embodiment of the present invention. FIG. 7 is an explanatory diagram of packet priority inversion due to “mismatch between packet priority and execution unit”, which is a problem in realizing packet priority control by software. FIG. 7 is an explanatory diagram of packet priority inversion by “two execution units of a task and an interrupt handler”, which is a problem in realizing packet priority control by software. It is a figure explaining the grounds of validity by priority control of a packet using interruption like packet transmission control device 1 concerning this embodiment.

  Next, embodiments of a packet transmission control apparatus and a packet transmission control method according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings may be contained.

(1) Functional Block Configuration of Packet Transmission Control Device FIG. 1 is a functional block configuration diagram of a packet transmission control device 1 according to this embodiment. As shown in FIG. 1, the packet transmission control device 1 includes an interface queue 20, a software interrupt handler 25, a transmission queue 30, a hardware interrupt handler 35, a communication controller 40, a software interrupt scheduler 100, and a task scheduler 150. The packet transmission control device 1 is mounted on a mobile communication terminal such as a mobile phone, for example. The packet transmission control device 1 implements packet priority control.

  The packet transmission control device 1 controls the transmission order of packets (specifically, packets PH, PM, PL) generated based on the application tasks 10H, 10M, 10L. In the present embodiment, for simplification of description, the priority at which the packet is to be transmitted is set to three levels (high, medium, and low).

  The application task 10H is processed in a kernel space in which processing common to the user space in which the processing for each application is performed and the operating system is performed in the software of the mobile communication terminal, and has high priority. For example, a task executed in the foreground by a user operation, such as browsing a web page, corresponds. The application task 10M and the application task 10L are also tasks that operate in the user space and the kernel space installed in the mobile communication terminal, but the priority of the application task 10M is lower than that of the application task 10H. Further, the priority of the application task 10L is lower than that of the application task 10M. The application task 10L (or the application task 10M) is a task for performing communication in the background where the user is operating the application, such as software update or incoming mail inquiry.

  The packet PH is a packet (high priority packet) generated based on the application task 10H, and has a higher priority to be transmitted than the packets PL and PM. The packet PM is a packet generated based on the application task 10M, and the packet PL is a packet (low priority packet) generated based on the application task 10L.

  The interface queue 20 is prepared for each network interface (for example, 3G system, LTE (Long Term Evolution) system, wireless LAN) provided in the mobile communication terminal. The interface queue 20 includes interface queues 20H, 20M, and 20L so as to correspond to the application tasks 10H, 10M, and 10L.

  That is, the interface queue 20H stores the packet PH generated by the application task 10H. Similarly, the interface queue 20M stores the packet PM generated by the application task 10M, and the interface queue 20L stores the packet PL generated by the application task 10L. In the present embodiment, the interface queue 20L constitutes a first interface queue that stores low priority packets (packets PL). The interface queue 20H forms a second interface queue that stores high priority packets (packets PH).

  The interface queues 20H, 20M, and 20L are independent of other interface queues, and a software interrupt handler 25 is assigned to each interface queue.

  The transmission queue 30 is a queue (buffer) included in a device mounted on the mobile communication terminal, specifically, hardware such as the communication controller 40 (or software such as a device driver). The transmission queue 30 can store the packets PH, PM, and PL output from the interface queues 20H, 20M, and 20L. The transmission queue 30 activates the hardware interrupt handler 35 (Top Half) when a free capacity capable of storing packets (packets PH, PM, PL) occurs in the transmission queue 30.

  Note that low-priority packets waiting to be transmitted in the transmission queue 30 cause the high-priority packets to be delayed. In the meantime, it is preferable to reduce the data size that the communication controller 40 can transmit on the communication path. In mobile communication terminals, the communication speed is generally much slower than the processing speed for software to store packets in the transmission queue 30, so the size of the transmission queue 30 is reduced to about 1 packet. However, since the frequency of execution of writing packets to the transmission queue 30 increases by reducing the size of the transmission queue 30, it is desirable to implement this by using the software interrupt handler 25 that has a smaller overhead when executing processing than the task.

  The software interrupt scheduler 100 executes software interrupt scheduling in consideration of the priority (high / medium / low) of the application tasks 10H, 10M, and 10L. Specifically, the software interrupt scheduler 100 stores the priority of the packets PH, PM, and PL generated based on the application tasks 10H, 10M, and 10L, and should be activated based on the stored priority. The software interrupt handler 25 is determined. More specifically, the software interrupt scheduler 100 is called after the execution of the hardware interrupt handler 35 that processes hardware interrupts from the communication controller 40 and within the task scheduler 150 in which the priority of the task being executed is switched. If there is accumulation of packets in the queues 20H, 20M, 20L, a software interrupt handler 25 (Bottom Half) for sending packets to the transmission queue 30 is activated.

More specifically, when the software interrupt scheduler 100 is activated from the hardware interrupt handler handler or the task scheduler, the software interrupt scheduler 100 stores the priority of the currently executing application task and the packet storage in the interface queues 20H, 20M, and 20L. The priority of the performed task is compared, and it is determined which of the interface queues 20H, 20M, and 20L the software interrupt handler 25 handler is to be activated. For example, the software interrupt scheduler 100 can be implemented as follows.

  In this way, when packets are stored in the interface queues 20H, 20M, and 20L, the priority of the task that stores the packets is managed as prio_high, prio_mid, and prio_low. In addition, when there is a vacancy in the transmission queue 30 and the software interrupt scheduler 100 is started from the hardware interrupt handler 35 or the task being executed in the task scheduler 150 is switched, the software interrupt scheduler 100 is being executed. Only the software interrupt handler 25 that performs the writing process of the packet of the interface queue having a higher priority than the task priority (prio_cur) is activated.

  That is, the software interrupt scheduler 100 determines the priority of the task currently being executed, the storage status of the packet PL (packet PM) in the interface queue 20L (or the interface queue 20M), and the storage status of the packet PH in the interface queue 20H. Based on the above, it is determined which of the interface queues 20H, 20M, and 20L the software interrupt handler 25 is to be activated. By such scheduling in consideration of the priority by the software interrupt scheduler 100, execution of the software interrupt handler 25 corresponding to the interface queue having a lower priority than the task being executed (priority inversion) is prevented.

  The interface queue 20H outputs the packet PH to the transmission queue 30 based on the activation of the software interrupt handler 25 for the interface queue 20H by the software interrupt scheduler 100. Similarly, the interface queue 20L (interface queue 20M) outputs the packet PL (packet PM) to the transmission queue 30 based on the activation of the software interrupt handler 25.

  In this embodiment, since only the software interrupt handler 25 of the interface queue having a priority higher than the task priority being executed is executed, the packet of the interface queue having a priority lower than the task priority being executed is Not sent out. Packets in the interface queue with low priority are low priority when the software interrupt handler 25 is activated in the task scheduler 150 where the running task is switched and the running task is switched to a task with a low priority. When the software interrupt handler 25 for the interface queue having is activated, it is sent in order of priority.

(2) Operation of Packet Transmission Control Device Next, the operation of the packet transmission control device 1 described above will be described. FIG. 2 shows a control operation flow of the packet transmission order by the packet transmission control device 1.

  As shown in FIG. 2, packets PH, PM, and PL are input from the application tasks 10H, 10M, and 10L to the interface queues 20H, 20M, and 20L, respectively (S10). Each application determines whether or not there is free capacity in the transmission queue 30 at the packet input timing to each interface queue (S20).

  If there is free space, the processing is continued, and the packet stored in the interface queue is written to the transmission queue 30 (S70).

  FIG. 3 shows operations of the application tasks 10H, 10M, and 10L when the transmission queue 30 has a free capacity. As shown in FIG. 3, for example, the high priority application task 10H storing the packet PH in the interface queue 20H writes the packet PH into the transmission queue 30 as it is. Application tasks 10H, 10M, and 10L are assigned processing priority in this order. Since the packet is written, the priority inversion of the packet does not occur.

  On the other hand, if there is no free space, the application tasks 10H, 10M, and 10L only input packets to the interface queues 20H, 20M, and 20L, and the free space is created in the transmit queue 30 without writing to the transmit queue 30. Wait until (S30).

  If there is free space in the transmission queue 30, the communication controller 40 generates a hardware interrupt handler (S40). After the generated hardware interrupt is processed by the hardware interrupt handler 35, the software interrupt scheduler 100 activates the software interrupt handler 25 for the interface queues 20H, 20M, and 20L based on the software interrupt from the hardware interrupt handler 35. (S60). Next, the packet stored in the interface queue is written in the transmission queue 30 according to the priority (high, medium, low) of the packet (S70).

  FIG. 4 shows an operation concept of the software interrupt scheduler 100 when there is no free capacity in the transmission queue 30. As shown in FIG. 4, when there is no free space in the transmission queue 30, it waits until there is free space in the transmission queue 30, and when there is free space in the transmission queue 30, a hardware interrupt from the communication controller 40 is sent to the hardware. The interrupt handler 35 processes and starts the software interrupt scheduler 100 after the processing is completed ((1) in the figure). The software interrupt scheduler 100 activates the software interrupt handler 25 for the interface queue 20M ((2) in the figure), and the packet PM stored in the interface queue 20M is written to the transmission queue 30.

  As described above, the output (write) operation from the interface queues 20H, 20M, and 20L to the transmission queue 30 differs depending on the empty state of the transmission queue 30. The execution of the hardware interrupt handler 35 and the software interrupt handler 25 has a higher processing priority than the execution of the application task, and even when a high priority task is being executed, a low priority interface queue (for example, an interface queue) 20L), packet writing to the transmission queue 30 can occur, so that packet priority inversion occurs. In the present embodiment, the software interrupt scheduler 100 described above compares the priority of the task being executed with the priority of the task that has performed the write processing to the interface queues 20H, 20M, and 20L, and then the software interrupt handler 25 ( Since the software interrupt handler corresponding to the interface queue is activated, such a priority inversion of the packet is prevented.

(3) Action / Effect As described above, according to the packet transmission control device 1, the software interrupt scheduler 100 switches the hardware interrupt handler 35 or task activated by the hardware interrupt from the communication controller 40. Called by the task scheduler 150 to control the activation of the software interrupt handler 25 for the interface queues 20H, 20M, and 20L. The software interrupt handler 25 preferentially writes the high priority packet from the interface queue to the transmission queue 30. For this reason, even when packet priority control is realized by software, such as a mobile communication terminal, it is possible to effectively suppress delay of high priority packets and deterioration of throughput.

  More specifically, according to the packet transmission control device 1, when the packet priority control is realized by software, “the packet priority and the execution unit do not match” and “the two execution units of the task and the interrupt handler” It is possible to solve the packet priority inversion problem caused by "".

  FIG. 5 is an explanatory diagram of packet priority inversion due to “the packet priority does not match the execution unit”. The software achieves the desired operation by sequentially processing the execution units of tasks and interrupt handlers, but if the "processing execution unit" and "packet priority" do not match, packet priority inversion occurs. obtain. In the example of FIG. 5, the interface queue is not classified by priority, and the low priority packet may be transmitted before the high priority packet depending on the timing at which the application inputs the packet to the interface queue. . On the other hand, in the packet transmission control device 1, as described above, the software interrupt scheduler 100 controls the activation of the software interrupt handler 25 for each interface queue according to the task priority being executed. It has been solved.

  FIG. 6 is an explanatory diagram of packet priority inversion by “two execution units of task and interrupt handler”. Software execution units include “task” and “interrupt handler”. The “interrupt handler” is executed by interrupting the processing of “task”. For this reason, in the example of FIG. 6, the low priority packet may be written to the transmission queue by the software interrupt handler, and the application task may be transmitted before the high priority packet being processed. On the other hand, as described above, the packet transmission control device 1 controls the activation of the software interrupt handler 25 by the software interrupt scheduling by the software interrupt scheduler 100 and writes the packet to the transmission queue 30 as described above. The problem is solved.

  In addition, with respect to priority inversion that occurs at the time of output (write) from the interface queue to the transmission queue, a process for outputting from the interface queue to the transmission queue is implemented as a task, and tasks divided according to priority are scheduled. A method is conceivable. However, since the frequency of writing to the transmission queue increases by reducing the size of the transmission queue to about 1 packet in the mobile communication terminal, the delay time is greatly affected by the overhead of the context switch when the task is realized. .

  FIG. 7 is a diagram for explaining the grounds of validity by packet priority control using an interrupt, like the packet transmission control device 1 according to the present embodiment. As shown in FIG. 7, in the case of packet priority control using interrupts, it can be seen that the activation time is significantly reduced (from 108.3 μsec to 7.4 μsec) as compared with packet priority control by a task. For the measurement of the processing time shown in FIG. 7, an armadillo 500FX equipped with Freescale i.MX31L was used as the CPU.

(4) Other Embodiments As described above, the contents of the present invention have been disclosed through the embodiments of the present invention. However, it is understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. Should not. From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art.

  For example, the embodiment of the present invention can be modified as follows. In the above-described embodiment, for simplification of description, the priority for transmitting a packet has been described as three levels. However, the priority may be four or more levels. Alternatively, the priority may be two stages.

  In the embodiment described above, the packet transmission control device 1 has been described as being implemented in a mobile communication terminal. However, the scope of application of the present invention is not limited to a mobile communication terminal, and packet priority control is performed by a software architecture. Of course, the present invention can be applied to other communication apparatuses to be realized.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is determined only by the invention specifying matters according to the scope of claims reasonable from the above description.

1 ... Packet transmission controller
10H, 10M, 10L… Application task
20, 20H, 20M, 20L ... Interface queue
25 ... Software interrupt handler
30 ... Send queue
35 ... Hardware interrupt handler
40 ... Communication controller
100 ... Software interrupt scheduler
150 ... Task scheduler
PH, PM, PL ... packets

Claims (5)

It has an interface queue prepared for each network interface and a transmission queue of the device, is generated based on the low priority packet generated based on the application task and the application task, and is transmitted more than the low priority packet. A packet transmission control apparatus for controlling a transmission order of high priority packets having a high priority to be
The interface queue is
A first interface queue storing the low priority packets;
At least a second interface queue that stores the high priority packet and is independent of the first interface queue;
The transmission queue can store the low priority packet output from the first interface queue and the high priority packet output from the second interface queue;
A hardware interrupt handler that processes hardware interrupts from hardware or a task scheduler that switches tasks, and includes a software interrupt scheduler that starts a software interrupt handler for the interface queue,
The software interrupt scheduler determines whether to activate the software interrupt handler for the first interface queue or the second interface queue based on the priority when activated by the hardware interrupt handler or the task scheduler. Packet transmission control device to be determined. The software interrupt scheduler determines the first interface based on the priority, the storage status of the low priority packet in the first interface queue, and the storage status of the high priority packet in the second interface queue. Determining whether to invoke the software interrupt handler for the queue or the second interface queue;
The second interface queue outputs the high priority packet to the transmission queue based on a software interrupt to the second interface queue by the software interrupt scheduler,
The packet transmission control device according to claim 1, wherein the first interface queue outputs the low priority packet to the transmission queue based on a software interrupt for the first interface queue by the software interrupt scheduler.   The software interrupt scheduler stores the priority of the low priority packet and the high priority packet generated based on the application task, and determines a software interrupt handler to be activated based on the stored priority. The packet transmission control device according to claim 1, wherein the packet transmission control device is determined.   The capacity of the transmission queue is reduced to a data size that the hardware can send on the communication path before the low priority packet or the high priority packet is stored in the transmission queue from the interface queue. The packet transmission control device according to claim 1. It has an interface queue prepared for each network interface and a transmission queue of the device, is generated based on the low priority packet generated based on the application task and the application task, and is transmitted more than the low priority packet. A packet transmission control method for controlling the transmission order of high priority packets having a high priority to be
The interface queue is
A first interface queue storing the low priority packets;
At least a second interface queue storing the high priority packet;
The transmission queue storing the low priority packet output from the first interface queue and the high priority packet output from the second interface queue;
Activating a software interrupt handler for the interface queue based on a call from a hardware interrupt handler or task scheduler that handles hardware interrupts from hardware,
In the step of activating the software interrupt handler, when activated from the hardware interrupt handler or a task scheduler for switching tasks, either the first interface queue or the second interface queue is activated based on the priority. Packet transmission control method for determining whether to activate a software interrupt handler handler for.

Images