Counter-based wide fetch management

Patent metadata

Field	Value
Publication number	US-2016299846-A1
Application number	US-201615186599-A
Country	US
Kind code	A1
Filing date	Jun 20, 2016
Priority date	Apr 15, 2014
Publication date	Oct 13, 2016
Grant date	—

Abstract

Embodiments relate to counter-based wide fetch management. An aspect includes assigning a counter to a first memory region in a main memory that is allocated to a first application that is executed by a processor of a computer. Another aspect includes maintaining, by the counter, a count of a number of times adjacent cache lines in the cache memory that correspond to the first memory region are touched by the processor. Another aspect includes determining an update to a data fetch width indicator corresponding to the first memory region based on the counter. Another aspect includes sending a hardware notification from a counter management module to supervisory software of the computer of the update to the data fetch width indicator. Yet another aspect includes updating, by the supervisory software, the data fetch width indicator of the first memory region in the main memory based on the hardware notification.

First claim

What is claimed is:

1 . A computer-implemented method for counter-based wide fetch management in a computer system that comprises a processor, a cache memory, and a main memory, the method comprising:
assigning, by a counter management module, a counter from a set of counters, to a first memory region in the main memory, wherein the first memory region is allocated to a first application that is executed by the processor; maintaining, by the counter, a count of a number of times adjacent cache lines in the cache memory corresponding to the first memory region are touched by the processor within a predetermined duration since the assigning of the counter to the first memory region, wherein the processor touches the cache lines in conjunction with execution of the first application; updating, by the counter management module, a data fetch width indicator corresponding to the first memory region in response to the count being at least a predetermined threshold value within the predetermined duration since the assigning of the counter to the first memory region; and assigning, by the counter management module, the counter to a second memory region in the main memory in response to the count being less than the predetermined threshold value within the predetermined duration since the assigning of the counter to the first memory region.

2 . The computer-implemented method of claim 1 , further comprising disabling the counter by the counter management module in response to the count being at least the predetermined threshold value within the predetermined duration since the assigning of the counter to the first memory region.

3 . The computer-implemented method of claim 1 , further comprising disabling the counter by the counter management module based on the elapsing of the predetermined duration.

4 . The computer-implemented method of claim 1 , further comprising:
determining, by the counter management module, that a predetermined number of fetches from the main memory to the cache memory have been performed from the first memory region since the assigning of the counter to the first memory region; disabling the counter by the counter management module based on the performing of the predetermined number of fetches; and in response, reassigning the counter to a second memory region in the main memory, the second memory region being distinct from the first memory region.

5 . The computer-implemented method of claim 1 , wherein the set of counters is stored in one of the counter management module and the cache memory.

6 . The computer-implemented method of claim 1 , wherein the data fetch width indicator is stored in a page table entry associated with the first memory region.

7 . The computer-implemented method of claim 1 , wherein the data fetch width indicator is stored in a memory-area property storage located in the first memory region.

8 . The computer-implemented method of claim 1 , wherein the data fetch width indicator is stored in a segment table entry.

9 . The computer-implemented method of claim 1 , wherein determining, by the counter management module, the update to the data fetch width indicator corresponding to the first memory region based on the counter comprises:
comparing the count to the predetermined threshold; and in response to the count being greater than or equal to the predetermined threshold, updating the data fetch width indicator to facilitate wider fetches for the first memory region.

10 . The computer-implemented method of claim 1 , wherein maintaining, the count of the number of times adjacent cache lines in the cache memory corresponding to the first memory region are touched by the processor in conjunction with the execution of the first application by the processor comprises:
based on a first cache line associated with the first memory region being evicted from the cache memory:
determining, based on a use indicator associated with the first cache line and a use indicator associated with a second cache line, the second cache line being an adjacent cache line to the first cache line, that the adjacent cache lines were touched;
based on the determining that the adjacent cache lines were touched, incrementing the counter; and
based on the determining that the adjacent cache lines were not touched, decrementing the counter.

11 . The computer-implemented method of claim 10 , wherein a use indicator of a cache line is indicative that the cache line was touched based one or more of a read access of the cache line, a write access of the cache line, and zeroing of the cache line.

12 . The computer-implemented method of claim 1 , wherein the data fetch width indicator specifies a number of cache lines to use for fetching data into the cache memory from the main memory.

13 . A computer program product for implementing counter-based wide fetch management in a computer system that comprises a processing circuit, a cache memory, and a main memory, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, wherein the computer readable storage medium is not a signal, the program instructions readable by the processing circuit to cause the processing circuit to perform a method comprising:
assigning, by a counter management module, a counter from a set of counters, to a first memory region in the main memory, wherein the first memory region is allocated to a first application that is executed by the processing circuit; maintaining, by the counter, a count of a number of times adjacent cache lines in the cache memory corresponding to the first memory region are touched by the processing circuit within a predetermined duration since the assigning of the counter to the first memory region, wherein the processing circuit touches the cache lines in conjunction with execution of the first application; updating, by the counter management module, a data fetch width indicator corresponding to the first memory region in response to the count being at least a predetermined threshold value within the predetermined duration since the assigning of the counter to the first memory region; and assigning, by the counter management module, the counter to a second memory region in the main memory in response to the count being less than the predetermined threshold value within the predetermined duration since the assigning of the counter to the first memory region.

14 . The computer program product of claim 13 , wherein the method further comprises disabling the counter by the counter management module in response to the count being at least the predetermined threshold value within the predetermined duration since the assigning of the counter to the first memory region.

15 . The computer program product of claim 13 , wherein the method further comprises disabling the counter by the counter management module based on the elapsing of the predetermined duration.

16 . The computer program product of claim 13 , wherein the method further comprises:
determining, by the counter management module, that a predetermined number of fetches from the main memory to the cache memory have been performed from the first memory region since the assigning of the counter to the first memory region; disabling the counter by the counter management module based on the performing of the predetermined number of fetches; and in response, reassigning the counter to a second memory region in the main memory, the second memory region being distinct from the first memory region.

17 . The computer program

Assignees

• IBM

Inventors

• Gschwind Michael K
• Moreira Jose E

Classifications

• G06F12/1009 Primary

  using page tables, e.g. page table structures · CPC title

• G06F12/0862 Primary

  with prefetch · CPC title

• G06F2212/602

  Details relating to cache prefetching · CPC title

• G06F12/0891

  using clearing, invalidating or resetting means · CPC title

• Y02D10/00

  Energy efficient computing, e.g. low power processors, power management or thermal management · CPC title