Compression store free-space management

In a computer system including a compressed memory wherein a unit of memory allocation can occupy a variable amount of physical memory space, a method of managing the compressed memory, said method comprising:

• determining an amount of current memory usage;
• determining an amount of memory required for outstanding input/output (I/O) requests;
• and
• managing the compressed memory as a function of the current memory usage and the amount of memory required for outstanding I/O requests.

A computer system for managing a compressed memory wherein a unit of memory allocation can occupy a variable amount of physical memory space, said compressed memory being a main memory unit of said computer system, said computer system comprising:

• means for determining an amount of current memory usage in said main memory and storing said amount in a continuously-updated counter;
• means for estimating an amount of allocated but unused memory;
• and
• a free-space manager, coupled to said means for determining and said means for estimating, for managing the compressed memory as a function of at least one of the current memory usage and the amount of allocated but unused memory, said managing comprising:
• setting at least one interrupt level and threshold, depending on one or more of measured and estimated quantities, including at least one of the current memory usage and the allocated but unused memory;
• and
• responding to crossings of said at least one interrupt level and threshold, depending on said one or more of measured and estimated quantities.

A computer system for managing a compressed memory wherein a unit of memory allocation can occupy a variable amount of physical memory space, said computer system comprising:

• means for determining an amount of current memory usage;
• means for determining an amount of memory required for outstanding input/output (I/O) requests;
• and
• a free-space manager for managing the compressed memory as a function of the current memory usage and the amount of memory required for outstanding I/O requests.

A computer system for managing a compressed memory wherein a unit of memory allocation can occupy a variable amount of physical memory space, said computer system comprising:

• at least one processor;
• at least one cache coupled to the at least one processor;
• said units of memory being organized as pages, blocks, and lines;
• a compression controller coupled to the cache and the compressed memory;
• a plurality of interrupt registers and a free-space list, coupled to said compression controller;
• means for determining an amount of current memory usage, coupled to the compression controller;
• means for estimating an amount of allocated but unused memory, coupled to the compression controller;
• and
• a free-space manager coupled to the at least one processor and to the compression controller, for managing the compressed memory as a function of the current memory usage and the amount of allocated but unused memory;
• said compression controller including:
• means for compressing lines which are cast out of the cache and storing the results in a number of fixed-size blocks drawn from the free-space list;
• means for decompressing lines on cache fetches;
• means for adding blocks freed by operations, including any of removing a line from memory, and compressing a changed line which now uses less space, to the free-space list;
• means for maintaining a count F of a number of blocks on the free-space list, said count being available to the free-space manager;
• and
• means for maintaining a set of thresholds in said interrupt registers, said thresholds indicating a size of F, wherein crossing said thresholds causes a processor interrupt;
• and
• said free-space manager further including:
• means for maintaining an appropriate number of blocks on the free-space list;
• means for dynamically setting one or more of interrupt levels and thresholds depending on one or more of measured and estimated quantities including the current memory usage and the allocated but unused memory;
• and
• means for responding to said interrupts and threshold crossings depending on said one or more of measured and estimated quantities.

A computer program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method for managing a compressed memory wherein a unit of memory allocation can occupy a variable amount of physical memory space, said compressed memory being a main memory unit of a computer, said method comprising:

• determining an amount of current memory usage of said main memory;
• storing said main memory current memory amount in a counter;
• estimating an amount of allocated but unused memory;
• and
• managing the compressed memory as a function of at least one of the current memory usage and the amount of allocated but unused memory, said managing comprising:
• setting at least one interrupt level and threshold, depending on one or more of measured and estimated quantities, including at least one of the current memory usage and the allocated but unused memory;
• and
• responding to crossings of said at least one interrupt level and threshold, depending on said one or more of measured and estimated quantities.

In a computer system including a compressed memory wherein a unit of memory allocation can occupy a variable amount of physical memory space, a method of managing the compressed memory, said method comprising:

• determining an amount of current memory usage;
• determining an amount of memory required for outstanding I/O requests;
• and
• managing the compressed memory as a function of the current memory usage and the amount of memory required for outstanding input/output (I/O) requests.