Data reading method and data reading apparatus

Abstract

A data reading method includes the steps of: a reading request issuing step of issuing a reading request for reading predetermined stored data; and a reading request re-issuing step of re-issuing a reading request when read data responsive to the reading request has not arrived within a predetermined time period, wherein: in the reading request re-issuing step, a flag is attached to the re-reading request, and thus, the re-reading request is differed from the first issued reading request.

1 . A data reading method comprising the steps of:
 a reading request issuing step of issuing a reading request for reading predetermined stored data; and   a reading request re-issuing step of re-issuing a reading request when read data responsive to the initially issued reading request has not arrived within a predetermined time period, wherein:   in the reading request re-issuing step, a flag is attached to the re-issued reading request, and thus, the re-issued reading request can be distinguished from the first issued reading request.   
   
   
       2 . The data reading method as claimed in  claim 1 , wherein:
 the issuance of the reading request is made for a data reading system in which an order of read data responsive to respective issued reading requests is not guaranteed.   
   
   
       3 . The data reading method as claimed in  claim 1 , wherein:
 the read data is in a form of a packet; and   the flag attached to the reading request is provided together with the packet in a state in which the flag is embedded in a not-yet-used area of the packet obtained responsive to the reading request.   
   
   
       4 . The data reading method as claimed in  claim 1 , wherein:
 a plurality of queues are provided for allowing a plurality of data reading requests;   a flag counter is provided for determining the flag to be attached to the reading request, for each queue; and   said flag counter is updated each time the data reading request is issued concerning the corresponding queue.   
   
   
       5 . The data reading method as claimed in  claim 1 , wherein:
 said read data is provided to a requester in a DMA transfer manner.   
   
   
       6 . The data reading method as claimed in  claim 1 , wherein:
 said read data is obtained with the use of an interface according to PCI-Express.   
   
   
       7 . A data reading apparatus comprising:
 a reading request issuing part of issuing a reading request for reading predetermined stored data; and   a reading request re-issuing part of re-issuing a reading request when read data responsive to the initially issued reading request has not arrived within a predetermined time period, wherein:   said reading request re-issuing part attaches a flag to the re-issued reading request, and thus, the re-issued reading request can be distinguished from the initially issued reading request.   
   
   
       8 . The data reading apparatus as claimed in  claim 7 , wherein:
 the issuance of the reading request is made for a data reading system in which an order of read data responsive to respective issued reading requests is not guaranteed.   
   
   
       9 . The data reading apparatus as claimed in  claim 7 , wherein:
 the read data is in a form of a packet; and   the flag attached to the reading request is provided together with the packet in a state in which the flag is embedded in a not-yet-used area of the packet obtained responsive to the reading request.   
   
   
       10 . The data reading apparatus as claimed in  claim 7 , wherein:
 a plurality of queues are provided for allowing a plurality of data reading requests;   a flag counter is provided for determining the flag to be attached to the reading request, for each queue; and   said flag counter is updated each time the data reading request is issued concerning the corresponding queue.   
   
   
       11 . The data reading apparatus as claimed in  claim 7 , wherein:
 said read data is provided to a requester in a DMA transfer manner.   
   
   
       12 . The data reading apparatus as claimed in  claim 7 , wherein:
 said read data is obtained with the use of an interface according to PCI-Express.