Method and system for determining copy-on-write condition
AssigneeNCR Corporation
InventorMark D. Campbell
Life of this patent
Estimating the term…
Abstract
A method for determining a copy-on-write condition in a UNIX process which includes providing a page table with an entry identifying a memory page location, and providing the entry with a copy-on-write bit. The bit is transferred to a circuit for processing and, if the memory page is to be written to and the copy-on-write bit is set, a copy-on-write fault is generated.
Claims8
A method for determining a copy-on-write condition in a UNIX process comprising:
- providing a page table with an entry identifying a memory page location;
- providing said entry with a copy-on-write bit;
- transferring said bit to a circuit;
- and
- generating a copy-on-write fault in said circuit if said memory page is to be written to and said copy-on-write bit is set to a predetermined value.
A method for writing data to a memory page in a UNIX process comprising:
- providing a page table with an entry identifying a memory page location;
- providing said entry with data access protection bits and a copy-on-write bit;
- transferring said bits to a circuit;
- and
- if said access protection bits allow said memory page to be written to and said copy-on-write bit is set to a predetermined value;
- generating a copy-on-write fault in said circuit;
- copying said memory page as a new page;
- and
- writing data to either said memory page or new page.
A method for writing data to a memory page in a UNIX process comprising:
- providing a page table with an entry identifying a memory page location;
- providing said entry with data access protection bits and a copy-on-write bit;
- transferring said bits to a circuit;
- and
- if said access protection bits allow said memory page to be written to and said copy-on-write bit is set;
- generating a copy-on-write fault in said circuit and providing said copy-on-write fault from said circuit to a status register;
- reading said status register;
- copying said memory page s a new page;
- generating an entry in said page table for said new page;
- clearing the copy-on-write bits for said entries;
- and
- writing data to either said memory or new page.
A method for managing memory units accessible by two or more processes on a computer comprising:
- providing a table with entry identifying a memory unit location;
- providing said entry with a copy-on-write bit;
- transferring said bit to a circuit;
- and
- generating a copy-on-write fault in said circuit if said memory unit is to be written to and said copy-on-write bit is set to a predetermined value.
A computer system, for running two or more UNIX processes having a shared memory page, comprising:
- a page table memory having an entry with a plurality of hardware control bits, software control bits and memory page address bits for said memory page, wherein said hardware control bits are connectable to a circuit which receives said bits and generates a control signal in response thereto, and wherein said hardware control bits includes access protection and copy-on-write bits;
- and
- a status register connected to said circuit for storing a copy-on-write fault whenever said memory page is to be written and said copy-on-write bit is set.
Dependencies are inferred from the claim text.